So certain are you?
Boba Fett Costume - The Dented Helmet Gallery
I thought it was pretty much decided we are looking at screen printed decals of some sort. Not painted on for sure on this ROTJ armor. The chest decal is the same.
Also, I dont know that I believe the PP2 was intended to be the ESB suit. It is not clear where the separation between the film and tour suits is but I dont believe any of the helmets or armor Sandy painted were supposed to end up on screen.