The paintjob is rather simple and quick: basecoat black, darkgreen wash, then successive layer of highlights, with some fine detail added (but not too much). I always feel Cthulhu should be as raw as possible, and that should reflect in the paintjob as well.
Fellow co-blogger (we post on this same blog) Bart also did finish his Cthulhu some time ago (as usual, his paintjob is a bit more sophisticated), so now we can have a battle of the Cthulhus (or is that Cthulhi?).
Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn.