6 hours in photoshop, using a photo reference and the hard round brush.

While painting digitally after a photo of a nude model isn't "the real" deal, or very original, I enjoyed working somewhat traditional. I didn't use any adjustment layers, effects, clipping masks or blending layers, just ye olde round brush. I didn't really time it, but my guess is that it took around 6 hours.
I quite like the outcome.

Oh and the ref was nicked from http://figuresfordrawing.tumblr.com/

Here's some process