TIPS ON METAL FOILING TECHNIQUES (CURSES, FOILED AGAIN)
By Marv Howell
Note: This is from a series of notes taken by Scott Sumsion, President, IPMS, Fort Crook Chapter, Omaha, Nebraska. Scott made the notes during a meeting and model demonstration on October 14, 1981. I have reviewed the notes and added any updates as of February 10, 1999. Marv Howell.
THE BASICS
Any brand of household aluminum foil can be used. Sometimes the cheaper brands are better because they are thinner. Try several and see which you prefer. Other metal foils will work equally well. These include things like candy wrappers, gift wrap foils, and even the really shiny mylars. However note with the mylar it will not bend to fit compound curves like metal foils.
Examine the foil to see what finish you will get from it. Most foil has a dull and a shiny side, "grain" and sometimes a texture. You can 
get variations in the finish on the model by applying the adhesive to the dull or shiny side, changing the orientation of a panel by rotating the foil, or using foil with a slightly different tone.
The Adhesive that I normally use is either Microscale or Superscale foil Adhesive. I have tried varnish, white glue, and future floor wax as an adhesive and they did not give good results.
For me, the best method to apply the adhesive is by a lint free cloth or a very soft brush. I have found that spray application causes the adhesive to bead on the foil and that will show up as bumps on your finished model. The goal is a very smooth layer of adhesive. If you can see ripples in the glue when it is dry, you will see ripples in your panel on the model. Try to "flow" the adhesive on to the foil. I pour a bit on the foil sheet and then spread it with the brush or cloth.
LAYOUT
Once you have selected the foil you want to use, lay it out on a smooth flat surface. A piece of glass or Plexiglas will work fine. Be sure it is as smooth as possible. The foil will pick up scratches, glue blobs, dirt or any other junk on the surface.
Prepare only enough foil for one work session. I usually work with a fairly small piece, about 8 inches by 10 inches or so. It is easier to handle that way. Use a lint-free rag to smooth the foil out on the glass and then tape the corners or the edges.
Now apply the adhesive, by brushing or rubbing it on in one direction. Then rotate the glass 90 degrees and apply a second coat. If you are going to be working with compound curves or difficult angles, a third coat will improve the grab in the adhesive. Note that you 
don't want to rub the under coats with the brush or rag as that will make blobs in the glue, be very gentle as you flow on later coats.
When the glue has dried from a milky appearance to a smooth clear finish, you are ready to cut and apply it. The adhesive works like contact cement. It will remain useable for several hours without loosing it's tackiness.
Cut the foil into slightly larger pieces than the panel on the model. Usually you will have a straight edge where you are butting up to a panel edge. Use a straight edge and cut the foil from the sticky side. A pair of dividers can help determine panel size and a good straight edge is important. Don't lay the straight edge on the glue or it will adhere to it. A VERY sharp exacto blade is important. If the blade drags or tears the foil, replace it. Cutting foil will dull the blade rapidly and the foil will then tear.
APPLYING FOIL TO THE MODEL
You are now ready to begin the foiling process. This works a lot like hanging wallpaper. Place your foil panel on the model panel to be covered. Start on one edge or in the center and work toward the end or to the outside edges. This helps to avoid wrinkles and tears. The point is to gently but firmly rub the foil down on the model. Be patient and methodical. This is not something to do when you are tired, angry or distracted by something else.
Use a tool to work the foil down smoothly. Remember you are working with a very thin and malleable metal. It can be gently persuaded and stretched a small amount to cover curves, rivets, panel lines, etc. The tools I use are Q-Tips, round toothpicks (blunted with sandpaper) and flat toothpicks cut to a chisel edge. Round paint brush ends can be useful also. Sometimes very small wrinkles will appear. 
These can usually be worked out by continued gentle firm rubbing.
When you are working with compound curves. The foil will sometimes begin to curl back on itself. You can make small slits in the excess foil when this happens to help relieve the stress in the foil and enable it to curve better.
When the panel is fully covered, burnish all the edges down firmly. Work the foil down around the rivets, into panel lines, and into recesses. This is what really pops out the detail. Now using your very sharp exacto blade, trim the panel to final shape. Use a straight edge, the panel lines on the model, or whatever is convenient as a guide for the blade. Carefully peel away the excess and that panel is done. Sometimes an edge will pop loose and will not burnish back down. A drop of crazy glue will help in that case.
Before you begin to lay an adjacent panel, you need to clean up any excess glue that was left where you peeled away the excess foil. It you do not do this, it will show under the next panel. I use a Q-tip dampened with mineral spirits to do this. Work away from the panel so the liquid does not get under the panel you just completed. Rubbing alcohol will also work to remove excess glue.
If you somehow have a thin sliver showing where two adjacent panels meet-up, touches of silver paint will usually work out fine.
If you really botch up a panel- tear it, find a big wrinkle, or some other disaster, just remove the panel, clean off the glue with alcohol or mineral spirits and put down a new panel. When you are working on major join line areas, such as wings or horizontal stabilizers, or other joins to major parts, work toward these joints from 
both sides and then trim the foil along the joint. This works better for me than attempting to cover the join line. The join line usually involves a major change of direction for the foil and that is difficult to do in one piece.
When covering wings or other airfoils, I recommend wrapping the foil over the leading edge when ever possible. Wrap it over from the topside and to some point on the lower surface where you can make a cut along a panel line. This makes a more solid connection of the foil to the model and reduces any problems with the foil pulling away from handling it. It also puts the cut line on the bottom of the model where any mistakes are less obvious.
If you have a really difficult area to cover, The lip of an intake, the very front of an engine nacelle, or a wingtip for example. It is sometimes better to just paint it. Sometimes you can work the foil in small sections to cover those really tight curves but usually paint will work out better in the long run and will give you another texture or tone to improve the model. Drop tanks would be another good example of something better painted than foiled.
If your model has major painted parts such as anti-glare panels, de-icer boots, or major stripes; paint those first and then foil up to them and trim the edges. Foil will adhere to painted surfaces, but it will also show up any imperfections in the paint, like grain, brush marks, etc. Foil does not take paint well at all, so attempting to put stripes or other markings over the foil is difficult unless the other markings can be done with decal.
FINAL DETAILS
You will find that decals adhere well to foil. However, they also tend to reflect edges worse than on a painted surface. You may want to revert to an older practice of trimming decals close to the design to reduce the clear area. This reduces the possibility that the clear will be an eyesore on your finished model. I have not found that any of the decal setting solutions affect the foil, so the small bits like data plates, no-step markings, etc can be set well with out major problems of trimming.
You can use metal polish, such as blue magic, on your foiled model. However remember that you may polish out the differences between dull and shiny panels and wind up with a totally polished model airplane. You are working with metal and it will do the same things as on full sized objects.
You can use overcoats on the foil, but it is not necessary. I would try it on a scrap of foil first. You would not want to spoil your finish if your flat coat or gloss coat beaded on the foil. I sometimes use a coat of Future floor wax to seal the decals and even out the surface.
Foil also makes an excellent masking medium. You can burnish it down around a curve (do not need to worry about minor wrinkles here) trim the curve or mark you need and paint as usual. In most cases, when you remove the foil you will find a sharper edge than you can get with tape.
Foil and eggshells are an interesting possibility. I have only tried the method of putting foil in with my boiling water for breakfast eggs. I did not get a very great result. However, It has been suggested that this will produce still another shade of foil to use for paneling models. When I tried it , the foil did discolor and darken, but it rubbed off as I applied the foil to the model.
SUMMARY
In this article, I have tried to cover some of the basic techniques I have found for working with metal foil. I hope that this has given you some ideas that you can apply to your next all metal model. If I can answer any questions or help you in any way with trying these techniques feel free to contact me at marvh@home.com.