For much of this step, I've moved the file into Painter. You can use Photoshop for this step, but I've found that I get smoother brushstrokes in Painter. There's an adjustable 'damping' factor at work in that program that helps to smooth out the stroke. Choosing a very small brush (either pencil or ink pen will do), Make sure that your brush is not set to pick up paper grain. "Soft Cover" will do. If you choose to remain in Photoshop, just take a very small brush, and set it to vary both opacity and size with pressure. Experiment, and set the brush softness to your liking. I begin the work of painting a few strands flying away in the wind. I keep one hand near CTL-Z (undo in both programs) to get rid of mistakes. For the strands flying into the breeze, there's probably one good one for every two that got erased.

I'm still working with just one basic color for now, just getting the form, or outline of the hair done. Experiment; this takes time. Don't fret if you find yourself erasing quite a bit of the hair away and starting over. Every new picture is a learning experience.

On the redhead, notice I've moved my sampling colors closer to her hair. Don't hesitate to move the palette wherever you need it.

A bit more work painting. Time to get the brunette's hair up to speed and caught up. I've erased some hair on the left, painted it back in, sometimes more than once. Added more hair on the right. You may notice some hair painted over her neck and shoulder. No problem. In this particular image, I plan on having all her hair behind her. What do we do? It would be tough to erase exactly along a line of her body. So, in Photoshop, I hold down CTL while clicking on her body layer. This creates an active selection exactly along the edge of her body. Then just grab your eraser (E) and erase the hair in front.