Sprinkle salt all over the pork shoulder, getting it into every crevice. Put the meat in a covered container in the refrigerator for at least 1 hour and up to 3 days. I like a solid 24 hours.
Rinse the meat and coat with the dry rub of your choice. If you're not using a dry rub, either use black pepper or pat the meat dry. Set foil in a tray that will hold the pork shoulder, leaving enough extra foil around the edges so you can wrap the meat later.
Get your smoker going. If you have lots of time, set it to 200F. A happy medium is 225F, but don't go higher than 250F. Set the meat in the tray and put it in the smoker.
Flip the pork shoulder every hour so it gets even smoke. Smoke like this for at least 4 hours, and up to eight; I prefer about six hours.
Now wrap the meat tightly in the foil and continue to cook until it's done and is shreddable, anywhere from another hour or two for a young hog or store-bought pig, to another eight hours for an old hog. You can do this in an oven, too.
Shred the meat with a pair of forks, and mix in the bacon fat. If you find yourself with long, stringy threads of meat, chop it a bit so it works better as a sandwich. Serve with the barbecue sauce of your choice on a bun with cole slaw.