You may also want to try a cut with a bone in it to give more flavor like pork shoulder. Not mention it tends to cost less. I always smoke pulled pork and that adds a lot of flavor. What I typically does is shred the pork and then add Rudy's barbeque sauce which is a sauce from a local Texas barbeque chain that is not sweet and slightly spicy then I add apple cider vinegar until is taste the way I want.

For the mustard rub I just season the meat then coat it in with cheap yellow mustard rap in plastic and let it set in the frig overnight. It doesn't taste like mustard at all but give the meat a nice vinegar twang. There are some recipes out that are lot more complicated and use more expensive mustard but I can't tell that they taste any different.