Prescott, AZ/blending of two geologic forms

Here I am blending two forms of rock in a short distance. Going from Clovis, NM to Prescott, AZ.
I carved extruded foam board with a paring knife and hotwire foam factory router tool and a medium/ coarse rasp file.
After Dave and I were satisfied with the formations, I gave the rockwork a plaster like slip coat to smoothen the surface of
the "rasped" foam. I continued to manipulate the slip coat as it was drying in front of a fan and becoming thicker. I would dip an inexpensive paint brush into water and paint over the slip coat with water to give the surface a smooth appearance.
Painting will be soon to come.