This is about the level I take my pencil underdrawings to - enough detail to base the powder and carbon on.

The first layers go down in powdered charcoal to start off with some value and texture.

I use the carbon pencil to work up details, value and texture! The Carbon pencil is great because it is more controllable than charcoal, but has its deep matte blacks.

I tend to save the eyes for last. Not sure why, but getting the rest of the image to a solid point is as important as the eyes, 

I build up color slowly using transparent layers in Photoshop, building up warm and cool tones until I reach the desired mood.