As Stalker says, I cover areas of charcoal which I might accidentally go over with my hand, whilst working, and then spray liberally with the fixative...
It seems to work well, but as far as presentation in sketchbooks, I'll cover with tracing paper to make sure that no smudging results.
Because I blend the charcoal though, this takes off the top surface, and so (I have found) makes the areas less prone to smudging.
I use both graphite and charcoal together now; graphite for lighter areas, charcoal for darker areas (and also carbon pencils to draw distinctions between the two in some places (such as for detailed shadow lines)). I certainly do really enjoy the charcoal, and ever since reading this book by JD Hillberry (who seems a great chap, BTW, from the brief e-mail contact I had with him) my drawing has improvedhttp://www.amazon.co.uk/Drawing-Realist ... 0891348689
It is odd, though, as I agree that the shine is a nice side-effect of using the graphite. For drawing purposes, graphite/lead is my favourite medium to use, and if it hadn't been brought to my intention that charcoal would work better for these dark areas, I would still be happily sticking to charcoal
Interestingly, when I was in contact with the aforementioned Hillberry, I had bought a set of pencils off of him. This included a 9B graphite pencil which doesn't produced any shine at all
So if heavy-shine in dark areas annoys you, then it's a brilliant pencil to use! (the shine is subjective though; to some it's like marmite, although I am indifferent about it).
Anyway, sorry to steer this topic away from your amazing drawing, Puff. I'm doing a-level Art at the moment, so your piece really interested me. I will point out that, personally, since using charcoal, my drawing has improved a lot.
edit-yes, hairspray works really well! I have artistis fixative too, and the only difference I've noticed is the smell (
) and that hairspray can make the paper slightly damper (although, I think it holds better!)