If your butcher has not already done so, remove the thin silverskin membrane from the bone-side of the ribs by working the tip of a butter knife or a screwdriver underneath the membrane over a middle bone. Use paper towels to get a firm grip, then tear the membrane off.
In a small bowl, combine the mustard, 1/4 cup of apple juice (reserve the rest), and the Worcestershire sauce. Spread thinly on both sides of the ribs; season with Traeger Pork and Poultry Rub.
When ready to cook, start the Traeger grill on Smoke with the lid open until the fire is established (4 to 5 minutes). Smoke the ribs, meat-side up, for 3 hours. Transfer the ribs to a rimmed baking sheet but leave the grill on. Set the temperature to 225F.
Tear off four long sheets of heavy-duty aluminum foil. Top with a rack of ribs; pull up the sides to keep the liquid enclosed.
Sprinkle half the brown sugar on the rack, then top with half the honey and half of the remaining apple juice. (Use a bit more apple juice if you want more tender ribs).
Lay another piece of foil on top and tightly crimp the edges so there is no leakage. Repeat with the remaining rack of ribs. Return the foiled ribs to the grill and cook for an additional two hours.
Carefully remove the foil from the ribs - watch out for hot steam - and brush the ribs on both sides with Traeger BBQ Sauce. Discard the foil. Arrange the ribs directly on the grill grate and continue to grill until the sauce "tightens", 30 minutes to 1 hour more.
Let the ribs rest for a few minutes before serving.