This image is made for a illustration project I am woirking on that should end up being a personal visual development book also representing skills as designer. Second part is that it is also made during the development of the photoshop brushes I am designing and can be found at my webshop http://digitalbrushdesign.bigcartel.com/
The brushes is made sow there is some for the shading like a large graphite powder brush and smaller brushes that you can manully precisely shade with and of course the stroke brushes.
Enjoy and feel free to ask question or too give your opinion.