
Here is a little on my process.

Start out with a sketch. I rarely draw in context. Meaning I will draw the individual designs separately on paper and then compose them after scan. It is not uncommon for me to draw faces and hands separately. Most of my drawings are about two inches in diameter for any given component.

I generally use the polygonal lasso tool to capture and flood fill my shapes in Photoshop. If I am not too concerned with the size of a file, I try to keep all of the different components such as hair, clothing, skin, etc.... on different layers.

If there is a background I repeat steps 1 & 2 for that. A lot of times I will use soft light layer to harmonize the colors. I have also found color balance to be good for keeping my warms and cools separate.

On a new Screen layer I will start putting in my lighting. For this first one I put in a warm sun light. I like to keep these layers separate from each other so I can change lighting as needed with the HSV sliders.

This image is just some more bounce light and ambient lighting from the sky.

Once I am comfortable with the general direction that the lighting and composition is going, I take it into Painter. Painter allows a better application of color and blending. I will use the eyedropper a lot for blending edges. I also use Ryan Wood's brushes and a couple that Sam pointed out to me.

After that I will kind of take it back and forth from Photoshop to Painter. I like to utilize and leverage the two against each other. I prefer Photoshops brush making abilities, and full screen tweaking. I use a lot of soft light layers and color correction for my work. I try to use auto levels quite a bit, just to see what the math says my colors and values should be. Then I will bring it back into painter for my edge and blend work. Painters brushes are superior in every way for the application of color for my sensibilities. The final step in a piece like this is to take it around the office and get everyone's opinions. Kevin Keele and Joe Olson generally comment on composition. Sam and Scott Stoddard will invariably talk about lighting and value. Ryan always talks about color response and textural quality. An Tom always points out my freaking tangents. It is a good crew to bounce off of.
Hope this helps.