colors are better handled as if real paint, large brush chisels the shape with a few colors side by side, then you can start working them together with more strokes to blend them while finding the form. Hair is best done with a large suggestive shape for each group, then break these down into smaller shapes with varying values, then get them ‘round’ and then add the detail - you spend less time swapping out brush sizes that way at least for the hair.
I like what you’ve done so far, very strong likeness in each