It indeed didn’t shrink, I’m happy to report
Once it had dried, I removed the masking tape along the edges to get the groundwork nice and square, then painted the frame with a medium brown, translucent furniture paint. I then applied some more masking tape and painted the whole base with a sand-coloured acrylic craft paint (much cheaper than modelling paint, the chief reason I used it
). I had to water it down a little to get it to paint easily over the rough terrain, using a large brush because this doesn’t really need to be done overly neatly — it just needs to cover everything.
When it had dried, I added an overall wash of a somewhat darker and browner sand colour of the same make, and while that was still wet, also some local washes of even darker brownish modelling paints that I blended into the “main” wash. All this added some shading to make the terrain look better.
After leaving this to dry overnight, I applied some artist’s pastels in a pale sand colour to some raised bits, especially the road area, and rubbed them in with my finger. Of course, most then promptly flew off again when I blew over the base, but enough stuck that it was worth the effort
After that I drybrushed everything with Army Painter
Skeleton Bone, another pale sand colour, to add more highlights and blend the colours together a bit.
I think I may have to repeat this with an even paler shade, though. After that, I’m not sure how to proceed yet. Much of this needs to be covered with grass, but I think my usual static grass is a bit short to achieve the effect I’m after. Suggestions are welcome