Re: Clean bottom how much?
If you can stand on the bottom while cleaning the bottom, you'll use a lot less effort. The diver that I use tells me he uses twice the air when he's not able to touch the bottom.
When I do it myself I try to work when I can stand on the bottom so I'll have two hands free -- one to clean and the other to check my work. It's very fast but occasionally I bump my head on the hull when surfacing for air. My wife is not thrilled when I come home with black CSC stains on my forehead.