I was surprised to find that the foamcore stands up to painting quite well and doesn't warp much at all. I used some old rowney poster paint to begin with but this had a tendency to dry with a powdery finish so when adding wet layers on top it tended to blend or streak.
I switched to some cheap artists acrylics, but these were a bit too gritty in consistency even though they covered reasonably well and suit my painting style which is to blend up from black.
My next experiment was with household emulsion. I bought some tester pots from a local DIY store. This made the boards warp when the paint was wet, but they flattened out a bit when they dried.
Walls & Floors
These were painted in two shades of grey, dark then a lighter grey top coat. I then drew on the mortar lines for the brick and cracked floor tiles in pencil, before giving them a black wash. The black wash was repeated in the corners and edges of the door tabs before the bricks were edgelined with a lighter grey.
Bricks and doors were drawn onto foamcore in pencil
I sketched out a few double door concepts on the computer just to give me an idea of where things like the hardware (hinges, lintels and straps) would go.
Brickwork was sketched out and then the whole door was painted in three shades of brown.
Right First Time?
As I wrote earlier, this was as much about experimenting in materials and techniques so it would be churlish of me to give you the impression that I got it all right first time, but I wasn't a million miles away.
In this earlier attempt I decided to go for a simple black and white checkerboard design with a red inlay on the white squares to give it a bit of an accent. My lining skills are pretty poor and not helped by the scabby brushes that now remain in my paintbox after my stepdaughter has been at them, time to invest in some new ones...
Now the basic technique has been cracked I'll be experimenting with some other features like stairs, a dias and maybe some other door concepts and different floor designs like lava and stuff...