Hahah. I used YOUR drawing, Mr Ploos. Just did some computer stuff to muck the colors aboot.
Charcoal is great. And you did a really good job on the drawing I must say. Good rhythm to the hair. Has a bit of a 1930s stylization that was big here in Depression Era -- dignity of the working man in hard times sort of vibe. The marks are dark and bold, which implies strong character.
So you needn't use any more than ya done. It's perfect as is without the highlights.
Don't forget you can also make lots of varied marks when and if it suits you. Charcoal is very flexible.
Another thing you can do, if you haven't tried it, is you can tone your paper with a smudging of charcoal rubbed over it before you do the drawing. That gives you a mid range. And as a way to do the highlights, you can take a kneaded eraser and pull out highlights with it. The neat thing about kneaded erasers is that they can be shaped to erase broadly or sharp.
Go + GO GO GO!!!!!!!
"Not a bit is wasted and the best is yet to come. . ." -- remembered from a dream