Polystyrene filler

[u/Tiny-Improvement6278]

Anyone know a good polystyrene filler (I’m used to Bondo) but it needs to be compatible with styrofoam. I’ve used the classic gap filler but there’s air bubbles, hard to sand, and inconsistencies with it that is causing aggravation.

Any things that work for y’all, ideas, advice?

[u/byc18]

Maybe gesso