Here's another sketch done in Photoshop CS6 on my Modbook at the Kline Academy of Fine Art in Culver City. The model is Lena and works with the Gallery Girls.
This was a 4 hour pose.
I didn't think that 4 hours was long enough to do anything but lots of black and white drawings but it was just one pose . Digital painting has its advantages like not having to wait for the paint to dry ,et cetera. But it also has it's disadvantages like showing correct color and having to deal with glare on the screen .
Sometimes not working at a consistent size gets confusing too.