Enydimon- Thanks. Yea well I dont know I struggle with this alot but generaly I try to figure out from where light comes from and where it hits the form. That point will be brightest and as the form turns around it gets darker and then just figure out what material and general color it is to what value range to use there( like I would use different value range for black t-shirt than for white). But yea I just improvise most of the time. I started looking at other artist I like and look for what exact values they use in different places. Someone like Ruan Jia, Stepan Alekseev on artstation and open their pieces and pick colors from piece and look at exact numbers and compare them :D
But as I said I dont understand it myself soo still trying to figure it out.
As for technical specific I just use one brush with lower opacity and just try to follow forms.
Yea when I start working on details (even in drawings) I sort of stop looking at it as a whole and just focus on little places :D Need to figure out something :D
Yea sounds like a nice exercise. Thanks for comment.
Some quick study, some longer copy and some sketches. Darkenned that character a bit but I found out I dont know how plate armor works in dim lighting...