Thanks for the kind comments!
The process was made alot easier with help of this hot wire cutting beauty by Proxxon bought for $89...
It makes short work of thining down thick sheets of foam to the correct widths for walls, platforms and floors. When you move the top wire anchor down the support rod, you can get 45 deg. cuts for wall mitering.
I heard most do stonework with an X-acto knife and then go over it with a dull pencil. Instead of a pencil, I use a regular screwdriver tip from a power drill, it also makes it easy to round-off the sharp corners of the stones by using the flat side and you can use it to press the blocks into the foam to make recessed stones.