After the hair, here are the shadows, the last step. I thought about a background, but I rather leave the full character this way.
So I went for high contrast, was pretty happy with the result but then I told myself it's too bad we can't read the boxer anymore. I decided to tone down the 100% black to 55% and voilà ! The result in the first image is striking, the global rendering looks great with the patterns on the boxer & the hair.
Might be another way to render for the next comic, I keep that in mind!