HARD COATING STYROFOAM! Cheap Way To Make Foam Props Strong (Big Halloween Pumpkins) - YouTube
UreCoat™ Product Information | Smooth-On, Inc.
EPSILON™ Series, EPS Foam Coating Epoxy | Smooth-On, Inc.
All Purpose Foam Coat - The Compleat Sculptor
Terrain idea: Tried to smooth styrofoam, turns out enamel spray and acrylic clear coat have some interesting cratering effects instead. Could be useful. That said, like any spray painting, do it outside.
EPSILON™ Series, EPS Foam Coating Epoxy | Smooth-On, Inc.
FoamCoat
Bulk All Purpose Foam Coat...
Hot Wire Foam Factory All Purpose Foam Coat, 25 lbs.