Monochromatic

Once you have your background painted, you can move on to the thing that's next furthest back. That might be your neck/shoulders, or your face. Notice how all of these students have their base color, a lighter tint version of their base color, and a darker shade version of their base color. I recommend having a brush for each color and possibly a 4th dry/clean brush for soft blending. Then you can paint your base color and darken it, lighten it, or both while it's still wet. Remember that dark values recede and light values come forward.