I completed a lesson on the torso this evening. That is very trying on the patience. The relationship of the ribs with respect to each other and the three dimensional shape of the figure is a very difficult thing to imagine. Superimposing it on a light figure was interesting, and helpful. I can see how forming these relationships helps with drawing a figure from memory. I can tell this is something that is going to take a lot of repetition to retain. I'm definitely going to revisit this lesson after I get through the entire body.
I need to be more careful about smudging too. Thankfully, this isn't a final piece.