I use Woodland Scenics dry transfer letters and numbers for a lot of my aircraft and armor that need special lettering or numbering. They come in sheets with varous sizes, colors include black, white, red, and yellow. If my memory serves, you want 45 degree Roman letters for military stuff. Unfortunately, they do not have the 60 degree letters/numbers.
I transfer (rub) them onto clear decal sheet, cut out to the edge of the letter, apply just like any other decal. Seal with Future or any other clear coat.