Master Study: Maku Felix

I've been following this artist for a while, I really like her style. Saw this sketch come up the other day and decided I need to sit down and do a masters study: http://matsumaku2013.tumblr.com/day/2013/11/14. I really like the sketchiness of the piece, I want to capture more of that controlled roughness in my own work.

Here's my study, but just the bust, not the whole body: