I decided to go against my usual method of always starting with the eyes, and instead started with the shell. After about three hours, I am just about finished with it. I used a base of 4B charcoal blended with a tissue to get the underlying tone, then added more to get the darker areas and blended with a stump. I went back over the dark areas with the 2B charcoal to get it nice and dark. I was a little worried that charcoal might not give it the wet, shiney appearance I wanted, but it seems to work. (Remember, this is my first reptile.)
This drawing is half the size of my previous works, so I expect it won't take as long. Now that the shell is done, I'm going to work left to right and do the hind flippers first. I'll save the sand he's lying on for last.