If you hang or let them rest for a few days which is fine in my opinion, first order of business would be to get the guts out and clean them up. I haven't got into waterfoul hunting yet but we kill and process our own chickens, after we kill them they get plucked and gutted. They then get washed out and put into the fridge for 2-3 days to rest, I've done the same thing with grouse. I will breast them out and snip off the legs in the woods, once home I will wash them clean and either filet the breasts off the bone or put them in the fridge on the bone for a day or so.