Make the brine: In a gallon zip-top bag, combine 4 cups water, ¾ cup apple juice, 2 tablespoons fresh lemon juice, 1 smashed garlic clove, ¼ cup kosher salt, and ¼ cup brown sugar. Seal and shake until the salt and sugar fully dissolve.
Brine the pork loin: Add the pork loin to the bag, press out as much air as possible, and seal tightly. Refrigerate for at least 8 hours, or overnight for the best flavor and moisture penetration. *If your half pork loin (about 4 lbs) is too long to fully submerge in a gallon zip-top bag, cut it in half.
Remove and dry: After brining, remove the pork loin from the brine and set it on a wire rack to drain and air-dry for a few minutes before seasoning. Pat it dry with paper towels.
Season the pork loin: Rub the neutral oil all over the loin as a binder. Season generously on all sides with the 3 tablespoons BBQ seasoning, then finish with a pass of the 1 tablespoon coarse black pepper.
Preheat smoker: Heat your smoker or pellet grill to 250℉ with your choice of wood or pellets. *We used Smokin' Pecan pellets, which is our preferred pellet.
Smoke to 120°F: Smoke the pork loin until it reaches an internal temperature of about 120°F.
Make the glaze: When the loin is almost to 120℉, combine the glaze ingredients in a small saucepan over low heat, including: ½ cup honey, 1 tablespoon hot sauce, 1 tablespoon fresh lemon juice, and 1 tablespoon butter. Bring to a low boil and let it reduce slightly.
Glaze and finish: Once the pork loin hits about 120°F internal, brush on the glaze and increase your smoker temperature to 350°F. Cook until the internal temperature reaches 140°F, then pull it off. *Since you're finishing the cook with the grill set to a higher temp, the loin should carryover cook to an internal temp of 145℉.
Rest before slicing: Let the pork loin rest until the internal temperature starts to drop slightly, which signals it's finished carrying over to about 145°F. Slice and serve.