I have experimenting with Kylon Glitter Blast Clear sealer as It does not attack foam. You do have to sand the board with something like 220 grit sand paper before applying any coating. Also you need to let any coating dry thoroughly at least 48 hours. Another primer I have tried is Krylon's prime coat for difficult surfaces. Both of these are available at Lowes Also don't put it on so heavy that It will soak through the paper and get into the foam. Anyway this only my ideas and a problem that I am not aware could appear. This is a question that asked Krylon and their answer: .
Thank you for taking the time to contact us. We are grateful to have a chance to help.
The Thompson's products, by nature, are "penetrants." This means that the product is not designed to dry on the surface or form a surface film. Instead, it is designed to remain relatively liquid, but disappear into the surface. If you apply our product over a surface that's not absorbent, it will remain tacky/oily.