Very nice work Mike. Here are a couple of tips that you might want to try. The light density foam that you use is great to work with, but is also prone to unintentional damage after it is finished. If you elect to replicate stucco over stone or brick try using Durham's Rock Hard Water Putty over the surface. This comes in powder form and can be mixed to a smooth consistancy and applied with a pallet knife. Just before it sets up stipple the surface very lightly with a boar hair brush. This will dry very hard and paint up very easily.
For your other surfaces you can also try this second technique to add strength and texture to the surfaces of your brick or stone. Mix up white glue, water and a touch of soap to lightly brush on the surface of the brick or stone surface. This should be a whole milk consistancy.Then take and old nylon stocking foot and make it onto a pounce bag. Fill this with either talcum powder (baby powder) or in some cases, pumice for a gritty surface and shake above the horizontal surface. As the material drifts down onto the surface it will bond to the white glue (PVA) and water mix and when dry it will create a more durable surface with texture. You can control even more specific textures by applying water based paints to individual stones and while wet, shaking some talc or pumic on the area.
One last tip...consider using chalk or pastels when you want fine coloring on the finished surfaces. After the structure is painted you can grind some of the colored chalk or pastels onto a section of cardstock and then use a brush to apply and feather various color for weathering.
Hope some of this is useful.
Joe, Ericka tells me that she hopes to start working on a chapter or two to have ready when I start on a real book. The one that I was approached to do was on modeling buildings, scenery and figures, but life has been pretty full these days and that will have to be on a back burner for awhile I guess.
All the best, Ken Osen