Some people swear by brine. I havent tried it and dont see the point. For a pork butt theres more than enough fat to keep the meat plenty moist while cooking. Some people brine to put flavor into the meat, but for me some smoke and a nice rub is all the flavor i want in the meat. I like meat flavored meat. Weird eh?
I dont wrap deer shoudler in foil. I polish off the cooking with some time in a crock pot, keeps it nice and moist. I would imagine that it would make sense after a few hours of smoking to keep the meat from drying out. Ive always done it the way I was shown. I would say that once the meat hits the 160-165 internal temp, thats the time to foil it. Thats when the fat inside the meat will start to let go and spread. Wrapped in foil should keep it inside. May not get as good of a bark on it, but im sure it would be fantastic.