Chris: Thanks for your comments. I really had a blast!
Your method of proceeding through the session is really valuable. I did something similar with measuring and placing landmarks. When she sat back down after the first 20 minute break, a lot was different. But I doggedly chased it!
Upon reflection, the things I don't like about what I did yesterday are her eye (too large) and the hard outline on the edge of her face. I also did it on junky paper which I will rectify in my next session.
What amazed me was that I was able to get any likeness at all!