Do a quick hand brushing to take off anything that's really loose, but don't bother beyond that. You're probably going to be going over it with a brush after anyway.
Remember that the anvil will start rusting again immediately after you take it out of the bath, so be ready to give it a coat of something to keep that from happening. A quick spray with WD-40 is good ("WD" = "Water Displacement"), as is drying off with paper towels and giving it a wipe-down with linseed oil, wax, or automatic transmission fluid.
As for which clamp goes where, remember that "+" = MORE and "-" = LESS. Put the "+" where you want more rust and the "-" where you want less rust.