Did the doc say anything about continuing to feed him? My guess is keep doing that til he feels better (all those meds) and starts eating more on his own. He might be just too tired sometimes to do that!

Do you have any shampoo that is gentle and not too heavily perfumed or anything? You could try that.

What kind of dish soap do you have? Someone on PT said there is a brand where the pH is the same as a cat's skin.

Maybe post this in Cat Health as well - you'll get way more feedback!