With a fairly tight sketch approved I move on to an "inking" phase. I bring the Photoshop sketch file into Adobe Illustrator to do the black linework. I reduce the opacity of the sketch layer and use the pen tool to "trace" the sketch. In the past I would then have to expand the linework and manipulate the shape anchor points extensively to accomplish the fluid line quality I am after. With the advent of CS5 however, we have the variable line width tool. This tool has dramatically streamlined my workflow. If you do any linework in Illustrator you should check it out.
The final Illustrator linework is then exported back to Photoshop where the outlined sections form the basis for layer masks of scanned in texture. With all of those imported and adjusted for color and density, it's back to the Wacom tablet to add shading and more color work. In addition to the dramatic speed increase of performing the technique digitally, I gain an ability to change or re-do sections that simply did not exist with the original painting style.