Looking back at my sketching work, I found that there was always a lot of uncertainty in the lines drawn on the spot and the shape of the figure was not well grasped, but on the contrary, the dynamics of the figure were much clearer and the lines were more certain when drawn on the computer.
The two beans method mentioned by the teacher was perfect for quickly capturing the dynamics of the figure. Once the lower crotch was identified, the rest of the figure was much easier to draw, and attention should be paid to the thickness of the lines, as the closer the figure is, the clearer it can be described, while the distant ones can be sketched in a few strokes.