Nice Character 32
Ambivorous, I took a stab at a value study from the ref you posted. I think you are quickly outgrowing the brush tool as your only means of mark making. Don't be afraid to use the lasso tool to better nail the shape. Value shape is what produces a likeness.
Also I should say your post 607 and 611 are good efforts. make more like those.
I used soft brushes for gradients and such, but if you absolutely wanted to, you could still stick to flat colors. This technique can actually be used to produce a finished product with strongly designed abstract shapes and realistic rendering on top. You could push an image like this further with texture brushes etc for that finish.