Fire up smoker with your favorite fuel source. Let smoker reach between 225 - 250°F.
Meanwhile, mix all dry rub ingredients, except yellow mustard, together in a stainless steel bowl.
Peel off silver skin from backside of ribs. Using a pastry brush, spread yellow mustard all over ribs. Then sprinkle rub on both sides of the ribs, covering mustard evenly to ensure they are well coated.
Place ribs into smoker. Once they reach internal temperature of 170°F, move them to a large piece of aluminum foil.
If using homemade sauce, coat ribs with brown sugar and Worcestershire sauce, spreading evenly. Add slices of butter and add root beer. Fold up foil and close tightly making sure there are no holes. (If using bbq sauce, simply coat evenly with desired amount of sauce and fold up foil around ribs in similar fashion.)