Here's the process behind my most recent poster for the Rose City Rollers.
1) Initial sketches sent to their Art Director, these were done separately and then arranged in Photoshop. Babs gave the okay so I moved on to polished drawings.
2) I decided to do the drawings in charcoal in order to force myself to figure out how to paint over charcoal drawings in Photoshop (yes, I really really really wish I was James Jean in his Fables years). I used so called "white charcoal" for the first time to tone down some of the stark blackness of the charcoal. I usually do my figures for the Rose City Rollers separately because the art director likes to have the freedom to move things around for all their print formats (posters, ads, signs, etc.)
3) I figured out how to paint on charcoal in Photoshop! I'm not going to describe it because its involvedish (mostly using a lot of layer masks) and I'm not sure how many people would be interested in it anyway. Needless to say, it works!