Uploading upon request.

I start with the sketch.

From there I create a new layer under it and block in the focal point(s) in a solid color, lock the opacity then start blocking in the base colors. I use an airbrush because the dithering effect allows me a greater pool of colors to select from when adding the details in the next layer..

In the next phase I created a new layer on top and while constantly using the color dropper to sample established colors I start adding in detail in the face. Some of the sketch layer is persists through the paintover and is much preferred over clean line art overall as cleanliness comes at the cost of sterility. Knowing the hair is going to be painted over still I bled the face out a bit. Be conscious of your layering to make things easier for you!

Next layer - additional details. IE hair/ cleaning up.

Not shown from the final image was the final overlay layer.... random puffs of thoughtfully chosen colors in order to unify it all and make the eyes and highlights of the the hair pop.