Chris Wahl is an illustrator living in Australia who has a wonderful blog. He has some videos on his site that show (in sped-up time) him doing some great drawing right in the computer. He uses the traditional blue pencil (in this case a digital “pencil”) underdrawing and then digitally “inks” in black over it. It’s great to watch him “undo” stuff he’s not happy with, reposition elements, and even flip the entire drawing backwards to get a fresh perspective on it, then flip it back again. It’s like taking a drawing to the mirror that you’ve been working on a while – it’s always a shock to see some glaring errors that you’ve just become used to, but are really apparent when the image is flipped. I’ve actually never thought, before this, to use the “edit>transform>flip horizontal” function in Photoshop to do the same thing.
The video is here to check out, and there are several more on his main page.