I don't hang geese or ducks because where I shoot them, they are often nice and fat. Fat goes rancid fast, so the general rule is to eat or freeze fat birds quickly.
Traditionally, it's pheasants, grouse and the like that are hung. They are lean birds and can use some hanging time. Most people will gut the birds in the feathers, then stuff clean paper towels in the cavity (loosely), then hang for a few days to -- if you're English -- a few weeks. I might try hanging a duck that was really skinny (wigeon are often this way) but never anything with decent fat.
Hope this helps,
I love all of God's creatures, properly prepared.