First of all, get a piece of scrap to test on. I tried some plane ol wal mart spray paint and it ate a hole right through my scrap piece of foam. I ended up using testors spray paint for models. It is made to be used on a large variety of surfaces, and I painted my foam phase 3 F-16 with it. Krylon makes a can of paint called "short cuts" and it says it is foam safe, but always test first. Buy a cheap piece of hobby foam from the arts & crafts store if you have to.