Ok I put the stray hairs idea in for you, basically it is a series of layers using the "#1" brush in photoshop or a very small brush, put in a few hairs at a time varying the type of brush and layer, screen, luminostiy, burn, darken, lighten etc. then vary the lighting on the layer and the opacity until it starts to look the way you want. Another thing to think about is shadows...pick up the color of the dark shadows around where the hairs are and brush in shadows on the face on a separate layer and then work them in a little. Also don't forget that the erase tool, using the brushes is a good way to work in the detail you want...this took about 10 min to do...