This is the lettering I've done on a pair of my firearms using white fingernail polish. Clean the surface, apply to the stamps or engraving gently and smoothly. Allow to dry. Use a towel with non aceton polish remover and using two or three strong strokes remove the excess.
Saiga 20. This job is actually several years old and has not been touched up. The logo or whatever russian klingon that is on the receiver is not faded or worn, I just didn't bother to 100% it. The old phrase of "it looks better in person" applies here too. The warm color lights muddles things in photos.
When 'illuminating the trades' I had first used the crayon method. While it looked great at first it did not stand the test of time. The crayon melted in the heat of summer in my cars trunk during range trips and it was soft enough either from firing and summer heat that it began picking up grime and coupled with heat and usage just didn't do that well. After the crayon had melted somewhat at times during cleaning it smeared leaving a thin sheen of the wax which caused me to avoid those areas during cleaning. So when I learned about the polish method I gave that a shot and I find that, IME to be the sturdier method.
Hi-Point 9mm Carbine. This is only a few weeks old. Worked well on the High Temp paint job I used on the receiver shroud.