SO I got this extra grey primer at home and thinking of dry brushing the buildings to have some natural feeling into it. But I actually don't know how I will execute this. I might mess up the figures.
PS: I have never actually painted any minis.
If you want a realistic feeling for the Santorini buildings, I'd recommend getting a special plastic primer like Fusion by Krylon. It will adhere better to the plastic of the game pieces. The type of plastic used for the game does not take paint very well.
Then go for a spray paint that has texture in it.
Followed by white spray paint.
Followed by a medium gray/brown wash.
Followed by lightly dry brushing white.
Followed by a matte varnish. (Or if you want extra protection, go with a gloss varnish first, and then hit it with a matte varnish)
You should probably then store all the individual pieces surrounded by foam core, but it's going to tend to chip with use.