Urthman over on the Flames of War forums has made a post about the process he used to create these great looking buildings.
I found it particularly interesting that he created the brick wall masters from high density blue foam. I’ve seen other tutorials that recommend scribing plaster walls for a brick effect which seems like a lot more effort than simply taking an xacto knife and a ruler to some foam. The other advantage of foam is of course it can be textured by pressing with various rough surfaces for a more worn look.
I will definitely have to try this for myself.