Charcoal is a very a pliable medium that you can push and pull endlessly.

Once I have a tight drawing with correct landmarks, I start with the darks and circle the head. Then I gently use a tissue over all to soften and start darkening the shadow side of the face. This will lighten the very dark areas required which always require several layers. I then use a kneaded eraser to lighten, often just pressing the eraser repeatedly or cross hatching with a small, kneaded eraser point.

​To darken, I use a Q-Tip or a pan pastel applicator touched on charcoal dust. The charcoal dust comes from sandpaper used to make points on my charcoal pencils. I like a strong and smooth surface like SOHO 135 lb. Acid-free drawing paper.  This paper is very smooth and tough and lets me lift with a kneaded eraser and blend repeatedly for soft and gentle transitions. 
Then stop before you ruin it. Less is often more!
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I really like the confidence in this image. It perfectly captures the child’s personality. Robert carries the presence of an old soul, a quality beautifully captured in his portrait. Looking into his eyes instantly washes away the surrounding noise, replacing it with a profound sense of calm and a steady, magnetic confidence​