I have found the best spray paint for terrain builders. It's affordable (About $5 a can), it does a nice even coat, and best of all:
IT DOES NOT MELT FOAM!
I couldn't believe it either. Rustoleum Flat Primer is what I have been searching for. I stumbled on the discovery when I was testing spray on primers for my Zone Mortalis tiles. They have foam parts, and I worried about the spray paint eating into them, and weakening my whole project. So I ran a few tests. I got a couple brands of craft acrylics and painted a coat on some pieces of foam, and used a spray paint I already had, Krylon brand, and this is what I got:
It ate right through the acrylic coat and into the foam. I figured I would need to do a couple more coats of the craft acrylics and test again, but I was running low on spray paint anyway. So I got into home depot and found the Rustoleum, thought I'd give it a try. Then I did the same test again, and got this:
This one looked much better. Then I noticed that it wasn't eating through the places where I didn't get the acrylic undercoat. So I got 2 pieces of foam (one pink and one blue) without paint on them and tried the spray:
I could not believe it. This is the stuff I have wanted all along. This makes my job so much easier. I was worried that I would need to paint in all the nooks and crannies of the tiles to get the foam, potentially covering up some of the details of the plaster bits with the thick acrylics. Now I don't need to. I took that can and sprayed about 5 tiles before it ran out.
They look so much better even just primed. Naturally I bought 5 more cans of this stuff then next time I found myself in Home Depot.