Well, I've gotten the base coat complete and started to add some shadows and highlights on the rock surfaces. After an hour or so of painting rocks, I realized it's going to need another coat of grey in several spots. About that point, I set the thing aside. I figured I'd let it sit overnight and start fresh on it (with a better light so I can see the underlying pink foam easier).

No one warned me how boring basecoating terrain can be. Oh well. It will be worth it in the end. On the bright side, I've just about figured out how I want to flock it.