Remove the pork shoulder from the fridge to rest at room temperature for up to one hour before smoking. Trim off skin and excess fat if needed.
Make the rub in a small bowl by mixing the brown sugar, salt, pepper, paprika, garlic powder, onion powder and optional cayenne.
Spread the mustard all over the pork shoulder with your hands. Then spread the rub evenly on all sides. Insert a wireless thermometer probe into the middle of the shoulder.
Heat the smoker to 225°F, add water-soaked wood such as apple or cherrywood as needed.
Once the temperature is stable, add the pork shoulder. Close the lid and adjust the vents for optimal smoke flow.
Smoke for 90 minutes per pound (about 9 hours for a 6 pound shoulder). The internal temperature should reach 185°F for slicing or 195-200°F for pulled pork. For a milder smoke flavor, wrap the meat in foil after 5 hours and continue smoking.
Remove the pork shoulder to a carving board and rest for 30 minutes to get juicier meat.
Slice the meat with a carving knife or shred using two forks (or meat claws). Serve with optional BBQ sauce!