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most of these are from drawing workshops with a live model though.

I think it's always a combination of everything. I can draw a lot from my head but typically that takes a much longer time so I set up as much as I can to get the image in my mind then the work is much easier.

Well... you have a very balanced mind for measures and proportions, it's amazing. Thank you for sharing your draws and techniques. I really think you got the lines ;)
Cheers.