>>11491461
>citadel stuff work on that materia
thats too expensive, use craft store shit, if directly painting onto the foam.

>Also once it's dry do I need to put a top coat over it to not ruin my toys by placing them in it?
I actually layer a bottom coat first, using this technique
https://youtu.be/bR-tgtcuRPg?t=576

>decided on polystyrene
make sure its extruded polystyrene and not EXPANDED polystyrene, expanded is that cheap shit foam packing peanuts are made of, and generally makes a terrible base for dioramas.