This kind of composition was new for me. I placed the horizon fairly low, leaving a very large, open sky. Sky and clouds have been rather neglected in many of my other paintings, so I figured it was about time that I dedicated more time to them.
One of the techniques that I found especially helpful for the rock face was glazing. I suppose one might call it more of an opaque glaze. Anyway, I began by sketching in the large rock with a slightly darker/more purple version of the local color. After that was dry, I went in with a darker warm purple and glazed over the entire rock. I was using Liquin and mineral spirits to thin it down. That glaze became the shadow in the recesses. When that became tacky (only an hour or so, as the Liquin sets up quickly), I went in with the orange highlight colors. I've found this technique gives a great sense of light, and I've done it on a number of my mountain paintings.
cadmium orange (just a tiny bit in the final highlights)
ivory black (just a touch to help neutralize some of the greens)