technique in making mountains. I want to make another module for taking pictures. The three pictures are of foam board. The first photo I painted directly to the foam. Seem to just soak in the paint. Do I need to put a light layer of joint compound before I paint. Any help will be appreciated. I have never used foam for mountains before, always just used plaster of paris and screen but that gets expensive. This second picture, I put silicone caulking between the layers to hide the cracks. Haven't done anything to this one yet.
I started plastering the foam and this is what I came up with so far. I still need to do a little touch ups and than paint.