If you have the artwork, there is a product called "tansfer medium" that brushes on printed artwork and once set, the paper can be wetted and rubbed off the back, leaving the ink behind. I used an old 70s Mod Podge version called Decal-it, I don't know that's the best (or the name) anymore. I used too many coats in anticipation of it being too weak for the paper removal, but it is actually quite strong; rubbery. A smoother surface might be had by spraying it (?). I can see my brush strokes, but only if I look close. I used the medium as the glue too.
I'll post a picture in a bit. (it's just a small PRR keystone taken from a magazine or catalog.)
