My 2 cents: First off, Boston butt is pork shoulder. Second, there is no need to pre rub, the butt will be on the smoker for (depending on size) 12 hours. So the rub will have plenty of time to get into the meat. I always coat with mustard to get the rub to stick. Last bit of advice: wrap the shoulder in tin foil once done. Pour in some oil/vinegar/rub solution. Wrap in a clean bath towel, and stuff in a cooler or microwave (if fits) for at least 30 minutes. I've left mine for 3 hours and it was still (almost) too hot to pull.