1. Wash the ribs and blot dry. Remove the thin papery skin on the back of each rack of ribs. (Pull it off in a sheet with you finger, using a corner of a dish towel to gain a secure grip.)

2. Combine the ingredients for the rub (paprika, black pepper, sugar, salt, celery seed, cayenne, garlic powder, mustard and cumin) in a mixing bowl and stir with your finger to mix. Rub the mixture on the ribs on both sides. Transfer the ribs to a roasting pan and let marinate for at least 4 hours, preferably overnight.

3. Set up the grill for indirect grilling (no heat directly under the ribs) and preheat to medium (about 350 degrees). Place a drip to sit under the ribs. If using a gas grill, place all the chips in the smoker box or smoker pouch and preheat the grill to high. When smoke appears, lower the heat to medium. If using a charcoal grill, toss the wood chips on the coals.

4. Place the ribs on the grill ove the drip pan and cover the grill. Cook the ribs until done, 1 1/4 to 1 1/2 hours. Start basting with mop sauce afte 30 minutes, basting every 20 minutes thereafter. If using a charcoal grill, replenish the coals after 1 hour. The ribs are done when the meat is very tender and it has shrunk back from the ends of the bones.

5. Transfer the ribs to a cutting board or platter. Mop one final time with mop sauce. Serve with your favorite barbecue sauce on the side.