I continue to do those drawing sessions on saturday mornings. For the moment I've seen a different model each time. It's interesting to see how, depending on the model, you feel more comfortable or a bit uneasy, and also, depending on your state of mind or level of fatigue, it will show up in the result.
It's a blend of high concentration and loose gesture, a mix of sticking to your favorite technique or daring to try different tools. It is interesting too to see what comes up when you completely let go.
I like the flow in the picture above, which was done in 6 minutes. Below, rightmost, is the last sitting the model did, she was a bit tired and had problems sustaining the pose, resulting in some shaking outlines that convey a nice movement to the sketch, I found.