I am doing a butt right now.... I use almost the exact ingredients of Bilbo's rub, with two additions, I rub the butt with mustard. I use a 50/50 mix of French's yellow mustard, and J/D Horseradish Mustard. Then I apply the rub seasoning.
But before that I inject the butt with a meat syringe. Today I used 2 cups Apple Juice, 3 Tbsp Franks Hot Sauce, 3 tbsp of my rub. I put it in a blender and mix good. I inject with the meat in a pan, then do the other steps above, then inject a few more times because movin the meat around the juice drains out of the meat. When I do this injection if you do it wrong the liquid just squirts back out of the meat, play with how you insert and you will discover there is a way to inject a little more juice without it squirting back out and the rub running off, this last injection is with my meat on the rack I'm smoking on, this way I do not have to handle the meat again it is already on the rack. Finally one more dusting of rub.
I hope you are Qhappy when its done.