What a sad story, I do hope Dave responds quickly, meanwhile please take Jay's excellent advice because he handles dozens of rescues and has seen it all before, believe me he knows what he is talking about. The advice you have been given already by others is good advice you should take seriously.
One point, when I first had my grey from a baby he was also petrified (it scared the crap out of me too!) of being sprayed with water but I persevered and kept it up twice a week, I set the nozzle to a fine mist and started by misting avove his head, just so it fell gently onto him like ultra-fine raindrops. I think you could start by doing this and your grey will gradually accept this, as he tolerates it increase the frequency until eventually every other day. Good luck and please keep us updated with your progress.