Choosing appropriate lighter/darker tones, we add more subtle highlights and shadows. For adding shadows, you can once again use an airbrush, multiply mode, ~10-50% opacity. For highlights, you can use the dodge tool, but be mindful of its strength. Its easy to over dodge.
During the previous step, a standard airbrush was used. From this point on, I use brushes C & D, at much lower opacities, multiple strokes. Brushes C & D are a little more gritty, so it reduces the ultra smooth airbrush appearance.
Try using the C brush (you may need to increase the size depending on the resolution of your image), overlay mode, 10-20% with varying degrees of dark orange red colors to add some life into the skintone. I usually do not cover the whole face with it. Just the outer edge, nose, lips, and eye areas. It usually gives it a rosy appearance. Also using the same brush mode I added the blue color to the eyes.
Also in this stage, you will want to tweak the highlights to the eyes, nose, lips.
Lets work on the hair. Using brush B, multiply mode, 70-100% opacity, use multiple strokes building them up. Using a lighter color will help since using mulitple strokes will Multiply on themselves. You will have to be cognitive of how you place the strokes. on the top left, it is only a build up of 3-4 strokes, whereas the bottom left is a buildup of many strokes.
After the majority of the strokes are placed, I usually use NORMAL mode and add some lighter areas like the strand on the right.
