A first attempt at a human face for the deer girl design I submitted a while ago - part of an ongoing commission.

Again, my experimental side shows - this was created using a lot less layers than usual (visible, at least): one for gray background, one for facial form and shading, one for hair form and shading, one for lighting, and one for color overlay.
I used pretty much only one brush - a custom brush made in SAI meant to replicate the stroke of a hard circular brush, which had pressure sensitivity assigned only to transparency. I called it the "sculpt" brush :P

Photo reference used, though no tracing was made.