When you are ready for your smoke, set the temperature to 250°F and preheat, lid closed for about 15 minutes.
Put pork shoulder directly on the grill grate and cook until the internal temperature reaches 160°F about 4-5 hours.
Layer four large pieces of aluminum foil on top of each other, ensuring they are wide enough to wrap the pork butt entirely on all sides. Then remove the pork shoulder from the smoker and place on the foil,
Begin wrapping three sides (closing one end) of the first layer of foil. Then pour apple juice on top of the pork shoulder, and a little into the open end. Wrap the remaining layers of foil tightly around the pork, ensuring the apple juice does not escape.
Place the foil-wrapped pork shoulder back on the grill and cook until the internal temperature reaches 200°F in the thickest part of the meat, roughly another 3-4 hours longer depending on the size of the pork shoulder.
Once to temp, remove from the grill and allow the pork to rest for 45 minutes in the foil. Then remove the foil and pour off excess liquid into a holding pan or bowl.
Place the pork a large cutting board or dish and for the first test, attempt to "slide" the bone out gently. If it pulls out smoothly, you know you've done a good job!
After shredding the meat, take the slightly cooled liquid and pour into a squeeze bottle. Use this to "re-hydrate" or further flavor the meat and feel free to use some more of the Rock's Coffee Rub to flavor to taste.