I took some time tonight to do the initial midtone and shading work with the airbrush. Unfortunately you can see that I was a bit over-judicious with the masking on his sleeve and back. I will touch this up with a brush but it's going to take a good deal of work to get the colours even now. Alas.
This second shot is just here to give you an idea of how it comes together with the composition. At this point I have to say that I am very, very happy.