So here is a small movie of the process I went through for my digital painting, Third Watch. You'll notice that at a certain point there is some backwards text in the images... this is because I decided to flip the painting about midway through, but im diplaying the movie all in the final orientation. The text doesn't even end up in the final piece. That's something I do a lot... flipping the image both horizontally and vertically, back and fourth. It helps a lot to spot anatomy, tonal and other issues. It can give you a fresh perspective. In this case, i just liked it better when i flipped it.
It was all done in Painter, with some very minor adjusting in Photoshop at the very end.
Third Watch - Process