I don't know about for dogs, but Glad Wrap's Press 'n Seal is the greatest thing for wrapping a human body part you can't get wet. Currently I'm showering sitting on a shower bench with my hammer-toe-repaired foot still bandaged, with it's "raincoat" of Press 'n Seal over top, and propped up on the edge of the tub.
I got the idea from a knee replacement website when I got my new knee 3 1/2 years ago.