Black and white faces: These are the most popular type that
I do. I use black markers for the drawing, and black prismacolor artsix for shading-- plus one or two background colors.
Using this method, I can usually draw one face in about four to five minutes. That means I can do 12-15 people per hour.
These take a little longer, but the results, using the color prismastix, have quite the wow-factor! I usually
can get through 8-10 people per hour using color. Oftentimes, I will draw all the guests at a party in black-and-white, but
the guest of honor gets treated to a color caricature.