Prepare the water pan and wood pellets in the smoker. Preheat the smoker to 225°F.
Remove excess fat from the pork loin and score the fat cap. Pat the pork loin dry and brush on a light layer of mustard or oil.
Mix all seasonings together. Rub the mixture on both sides of the pork loin, using your fingertips to work the seasonings into the meat.
Place the pork on a grill pan or directly into the smoker. Smoke for 2-4 hours, or until the pork loin reaches an internal temperature of 145°F. If desired, wrap the pork loin in butcher paper or foil for the last 30-60 minutes of cooking.
Rest the pork loin at room temperature for 15 minutes before serving.