Is it possible to use very thin black tape either on the foam or on the hotcoat to create pinlines. Instead of using ink, could the tape emulate the pinline?
I’ve used 3M pinline tape under the glass many times. Auto supply stores have it and it comes in 1/8" or 1/4" width. Sticking to foam is a bit hard so when you put it on try not to stretch the tape. It comes off if you do.