I usually brine waterfowl, - pluck and draw the guts while still warm, rinse, and put in an ice water bucket that has a few tablespoons of salt added. Keep refrigerated or in a cold outbuilding near freezing for 3 days and up to 5 or so. Makes the meat more tender, the same as hanging big game or beef does. The salt helps keep the meat from growing bacteria while in the water, and draws out excess blood. The time ageing relaxes the muscles and makes meat more tender. rinse before final preparation for cooking. I would not hang any birds with guts in, gut shot or not. I do hang upland birds for a few days, feathers on, at 4°C after drawing the intestines.
The toughest meat comes from stripping warm breasts off the bone and then freezing immediately. The meat will shorten in rigorous mortis when off the bone, and has no time to relax again. Not a problem if you use in ground meat, slow cooked stew, or fine sliced stir fry. i think the legs are a very important part of the duck, and especially of goose. Stewed they are wonderful. The best book i've found on cooking ducks and geese is called "Duck Duck Goose" and is available at McNalley Robinson.