It looks good, Jamie!!
I had read a lot of tutorials of figure painting and much of them reccomend red sable brushes. I read too Windsor & Newton has ones of the best (and expensive) brushes.
I reccomend S.Paine book "Building and Painting Scales Figures"
http://www.amazon.com/Building-Painting ... 0890240698
The book talk much about oils, not acrilic, but the basics (specially how and where to put shadows and lightings) are OK for me.
This tutorial for faces, by Calvin Tan is very good too:
http://zyclyon-tutorials.blogspot.com/2009/03/1_28.html
I don't know if Calvin talk about brushes in his main blog: http://zyclyon.blogspot.com/
Waiting the final stage
Darío