The first picture is about 25 minutes, very loose, not too much detail. I was trying to keep in mind - work large and light, slowly add your darks and intense colors. I did not sketch with pencil, just went right in with paint.
The second drawing, same viewpoint, is a bit tighter (maybe I was tense because we were listening to Obama's State of the Union address while we worked...you never know...) and I started with watercolor pencils, sketching the figure first, then adding washes of paint. I liked it until I started playing with her profile too much. Unless the face is spot-on, it's very distracting. I should have kept it a bit more mysterious.
The next evening I did draw one 20-minute pose with periwinkle charcoal pencil - this was a beautiful back view with lovely shadows. The weight of the figure did not feel "right" until I established the position of her feet and their cast shadow on the carpet.
Since that first painting felt a little tight, I just shifted my viewpoint a little and started another piece, this time trying to be more abstract, letting myself enjoy the paint rather than try to control everything. I like it. The photo is not great, the colors are a fresher and brighter in person. (this is not an invitation for you to come and see it in person...I'm just letting you know)
Finally for the last 20 minutes I moved toward the back of the model, quickly capturing the beautiful light and shadow on her back. My whole approach was lighter and less tense...I didn't have much time, so I just went for it! I chopped off her head because it was - well - awful - but this part is not too bad!
Practice, practice practice :)