Everything went much better today - started by quartering off the image to find the center and doing a line sketch (which was way too big at first). Kept fixing that until it looked right, then it was a pretty easy matter to start painting in the values. Lol, went with a much simpler composition than the Tiepolo this time too!
It's a Kent Williams painting that I admire for the bold handling and aggressive painterly work, though he was still able to capture the sitter's personality quite well. There's a single strong emphasis on her face, the darkest dark (eye hollows) right under the lightest light of her bangs, and the entire head is painted much more completely and subtlely than everything else. The rest of the comp is kept very economical and simple for contrast.