You definitely have your work CUT out for you ;-1
3 steps to consider in order to streamline the process, are to first get
all the mid-tones done before you, second fill in the darkest darks, and
finally bring the furthest points outward with highlights.
Food for thought:
The darkest and the lightest areas will attract the
eyes first, and a highlight will always look brighter right next to a shadow.
Enjoy the process