Locally a lot of the guys use a concoction we called Achie Goop to use as basic ground material on top of plaster cloth or paper. Dave Acheson is the progenitor of this mix and it works very nicely over just about any substrate. Achie Goop 1 cup Celluclay 1 cup Mold-a-Scene plaster 1 cup latex paint (this sets the color of the ground surface) 1/2 cup Elmer's glue 1/4 cup Perlite (Miracle Grow sells it cheap) this can be crushed finer if desired 1/4 teaspoon of salt (improves conductivity for using an electrostatic flocking tool) Mix well. Water added while mixing to the consistency of creamy peanut butter. Achie Goop spreads easily with cheap coarse bristle brushes and can be used to build up over broken ceiling tile to develop terrain. It can be wetted while working to add various forms of ground cover or flock. Attached are some pictures from local modeler Mike Borkon's Union Pacific Third Sub, Road of the Streamliners layout illustrating some of what can be done. I have become the Master Ballaster and Mother Flocker on his layout. In the past three Thursday work sessions, I have laid 186 feet of double-track mainline ballast, with about twice as much to go.