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.
How to Coat Styrofoam | ehow
Styroplast Foam Coating |...
All Purpose Foam Coat | Hot...
Hot Wire Foam Factory All Purpose Foam Coat, 25 lbs.
UreCoat™ Product Information | Smooth-On, Inc.
All Purpose Foam Coat | Hot...
All Purpose Foam Coat | Hot...
All Purpose Foam Coat | Hot...
FoamCoat
Foam Coat
Smooth Foam Bells Available in 4 Sizes Hollow Core EPS - Etsy