A recent "Simpit" discussion was about how to letter those little pushbuttons in your cockpit. That resulted in a variety of solutions being posted by several members. I will put those solutions that I remember on this page. If you happen to have a different solution to this problem then don't hesitate to let me know at speedone@chello.nl

1. Just use those regular transfer-letters available everywhere. Rub them on with a hard object. Advantage: many fonts, sizes and colors available. Disadvantage: they are generally not very durable and pushing them often will wear and tear them rapidly. This problem may be (partly?) overcome by putting a good quality varnish on top.
2. Use a sheet of self-adhesive transparent paper and print the letters on. Now stick the print on the button, that's it. Advantage: You can make it in all shapes and sizes you want, create your own symbols etc. Disadvantage: can't make white letters, although this can be overcome by using non-transparent white paper!
3. Similar to number 2 but this time you don't use a self-adhesive sheet. Some buttons come with a transparent cap that can be removed and then replaced (after you put the printed piece of sheet inside the cap). Advantage: see 2 plus more durability. Disadvantage: see 2, and this is obviously only limited to buttons that have these special caps fitted.
4. Use self-adhesive "sticker"-letters. Advantage: very easy to apply and change. Disadvantage: very limited number of fonts, sizes and colors available.
5. Same as 4, but this time the letters are used as a mask, and you use paint. First you (spray-)paint the button in the color you want the letters to be. Then you apply the sticker-letters. Now you paint the button again with the letters still on it, in the color you want the button to be. Remove the letters and voila.... Advantage: very durable. Disadvantage: limited to the available fonts and sizes. Not applicable to many buttons that will get "glued" together by the paint.
6. A method mentioned by Napalm (Mike): I use Model Railroad lettering dry transfers, available in a wide range of sizes and fonts, after you transfer to the button, use polyurethane or clearcoat acrylic on the button, if you don't want them glossy, you can stuff the modelers use over their transfers, don't remember the name of the stuff, just ask the clerk and he will know what you mean. Advantage/Disadvantage: I don't know ;-)
There are probably still many more methods out there, and if you know one please share it with us. What you need to do before using any of the methods, is thinking what your priorities are. Do you want backlit buttons? Are the buttons functional or merely esthetic? How often will you use them? etc. etc. etc.