Shading

I wanted to replicate the shading style of the original image, and to do this I used various brushes to emulate the style.

This is the initial shading I did with the blob brush tool. When I added all the basic shades, I then made a series of brushes to give a dithered look on the shading.

These are my brushes that I made. I did this by making small dots with the blob brush tool and selecting them all to make a scatter brush. This would make the brush strokes very dotted, thus adding to the dither effect.

These are two examples of the brushes to blend the colours. On the black, I only used two shades as the original poster has two shades on the woman's clothes. For the clouds however, I used many different shades of brush so they would look much more blended.