I don't really see how it could't be useful; it's essentially life drawing combined with environment study and colour and light practice... So long as you aren't colour picking and obviously do the sketch yourself it's extremely useful! Also handy for improving your flow and speed, especially if you set deadlines.
Hey man, these studies of yours are great! Just wonderin', are you using screenshots of the movie as a reference for the whole time? Just that, these pieces got quite a feeling in 'em, and I think this kinda practice could do good for me too! If you could explain your study-method a lil, I'd really appreciate it!
Cheers man. These studies are based off film stills; I find it useful for practicing colour, lighting, character interacting and so on at the same time. I'm basically trying to get the image as close to photo real as I can in 2-3 hours max. Probably going to livestream one soon so perhaps that'll be useful!