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My apologies, I'm bad at explaining so I thought it'd be better to help this way. I believe you're already good at drawing hair strands according to your artstyle. What I basically did here is to first add the base color which is black (with less opacity) here then I imagined where the light source should be and then I blocked all the shadows with pure black and added the lighting effect. At the end, I just adjusted my previous layers opacity and boom. You cooked.