I have finally got more comfortable handling oil paint. Instead of just mixing my colour and laying it on, I have now been dabbing relatively dry touches on top of the base layer, and using a broader dry brush to scatter the paint around a bit.
Using this technique I created blue, green and orange areas in the mountains in my painting above. This was closer to the amount of control I had in my pastel drawings, where I was able to shape mountains by carving out areas of light and dark. I will work on the mountains again to give them more depth now that I know what I’m doing.