EVA foam is soft, easy to carve, and flexible! It can be shaped with a heat gun and textured with a dremel tool! It can be easily painted with just about any paint you can get your hands on too! If you need something firmer, insulation foam boards are basically much thicker foam core and can be shaped with carving tools and a dremel, but not heat shaped. It also can't be exposed to paints like spray paint because it corrodes the foam! For smaller shapes (I used to use this for Homestuck horns back in the day) you can use floral foam! It doesn't take detailed carving very well, and it's super porous so covering it with something like Worbla, plaster, or even paper-mache is best before painting it. For foam wigs, like my Alastor wig, I used craft foam sheets you can get at any store! It's just ultra thin EVA foam, so that wig is heat shaped and painted with acrylic.

EVA foam needs to be heat sealed before it can be painted, which is just taking a heat gun and applying heat until the foam is shiny to look at. This closes up the pores and keeps it from soaking up the paint like a sponge. Plasti-Dip is my personal favorite to start with as a base coat; it's a rubber-based spray paint that closes any missed pores and creates a great surface to start painting on. I also personally don't like using spray paint on textured or detailed foam pieces because it's easy to miss spots, so if you have the patience I would recommend hand painting with acrylic.

Mod Podge, white glue, or clear dry liquid latex are all good choices for a sealant, but can all crack to come extent. If you're worried about cracking, I recommend Maker's Magic, Americana acrylic spray, or any non-enamel based coating!