I went to a croquis course every Wednesday for half a year in 2014. It was a very busy time for me, as I was busy with courses on my PhD, and I had chosen to attend Japanese lessons on Tuesdays as well. However, it was refreshing to go somewhere else with people of a very different background, and just draw for 2 hours. Every second lesson we had a model posing naked, and the other times we took turns posing (with clothes on). It was surprising how much easier it becomes when the clothes are not there! That said, drawing an entire pose in a few minutes (even without clothes) takes some practice. The first couple of times I did croquis, I didn’t finish drawing the whole body before the time ran out. But with practice, I ended up being able to include the whole body every time, even if we did a 1 minute pose. At times, I would also get the proportions right. ^^
Sometimes we had a few minutes to quickly sketch the important lines (2-5 mins):
Other times we got 10-25 minutes:
We also did some weird things where we had to draw with the other hand, not looking at the paper, without lifting the pen, or with doodles:
I learned a lot from doing croquis which I could never have learned just by copying photographs. I will definitely do this again sometime when I have the time, and I can highly recommend this for anyone who loves drawing and likes a challenge.