I did a Photoshop painting class/demo showing a lot of the basic techniques I use to paint quickly. I started out with some reference collecting, then a quick layout and color key before I demonstrated creating the final painting in the class.
I made this custom brush shape to paint the mountains.
Reference gathered from internet sources.
Color key, working with as large a brush as possible.
Final painting done in Photoshop CS5 on an Intuos 3 tablet, about 2 hrs.