This is an integral part of the illustration process when you are dealing with digital art work. Although working by hand is more expansive from a conceptual level for me, I normally go digital when it comes to creating the line art and making smaller revisions to an established sketch.
I’ve been using Photoshop to go over my hand-drawn sketches for years but I recently found out about new software called Sketchbook Pro. I just downloaded the 15 day trial version but I think it may be a new must-have.
My process is to hand-drawn sketch or storyboard and go over it with my graphic tablet pen to create digital line-art. I never really liked the photoshop pencil tool because it was a little too choppy. This new software seems more sensitive to my hand movement.