owch. well, i hate to say it, but your fish is probably on his way out. a fish that loosed his scales is exposed to all sorts of nasty things, and loss of scale is like losing a skin.
all that may help is a small bit of aquarium salt to improve gill function-it may increase his lifespan by a few days. keeping all microbes out of the water is something else you can do...putting antibacterials  in the water should help. also, putting "stress coat" in the water to try and help the mucus covering on your fish may have some effect.