Value study - The quick study is useful to set the composition and create atmospheric perspective (depth). This part of the painting only takes a few minutes. If it doesn't work, I haven't wasted a lot of time.
The color pass and some detail - During this stage I paint with a lot of texture. I also develop temperature of light, reenforcing warm sides and cool sides. This could use about another hour of detail if I was to take it to finish.