Here I have started to add some hair. I needed to get the skin tones below his hair sorted out. Too dark and you wouldn't be able to differentiate between his hair and his face. Too light and there would be no hair shadow.
Here I have added a shadow line to the left side [his left] of his face.
I still have some tweaking to do but I will wait and see what it looks like when finished, so I can have a good look at it.
I like to take lots of photos. You tend to see more on a photo.