Mold filler?

Hey everyone. So I’m making a mold at the moment, and am trying to remember the name of the filler I’ve used previously on ID models. We’ve tried using epoxy with microballoons, but the results of that are atrocious (it’s much, much too hard to sand reliably when it’s on top of yellow foam). I’ve used a type of plaster (I think it’s plaster) in the US, it goes on pink when it’s wet and then steadily turns to a chalky white substance when it’s dry. Anybody have any ideas?


EDIT: Just found out, it’s Drydex spackle. Is there a UK equivalent and is it strong enough to take a mold off of without tearing the whole piece apart?

we use to use joint compound first (over the foam) then prime with automotive primer and wet sand the primer for a smooth polished finish… then final paint coat.

Cool, thanks a lot. Do you know what grit you wet sanded with?

i think it was 320… here’s what I found on home depot