To marinate the ribs: In medium bowl, mix the brown sugar, paprika, black pepper, cumin, and cayenne pepper. Place the ribs on a large baking sheet and rub the ribs with some salt. Sprinkle the spice mixture evenly all over the ribs and massage the spices into the meat. Cover and refrigerate for at least 12 hours.
(about) kosher salt
apple cider vinegar
Apple-Bourbon Barbecue Sauce, warm
To barbecue the ribs: Prepare an outdoor barbecue for low cooking over indirect heat: For a gas barbecue, place the foil pan over one or two burners and half-fill the pan with water. Turn on the remaining burner(s) and heat the grill to 300°F. Spread 1 cup of the drained wood chips on a piece of heavy-duty aluminum foil. Place the foil directly on the lit burner and wait until the chips are smoking before you add the ribs to the grill.
For a charcoal barbecue, place the foil pan on the charcoal grate on one side of the barbecue and half-fill the pan with water. Build a charcoal fire on the other side and let it burn until the coals are covered with white ash and you can hold your hand just above the cooking grate for 4 to 5 seconds. (To check the temperature more accurately, cover the grill and drop a long-stemmed metal candy thermometer through the top vent; it should register about 300°F.) Sprinkle 1 cup of the drained wood chips over the coals.
Combine the vinegar and 3/4 cup water in the spray bottle. Season the ribs with salt. Place the ribs on the cooking grate over the water-filled pan. (Don’t worry if the ribs extend over the pan, as the pan will still catch the majority of the dripping juices.) Grill, with the lid closed, turning the ribs over and spraying them every 45 minutes or so with the cider mixture, adding another cup of drained wood chips at the same intervals, for about 3 hours, or until the meat is just tender. For a charcoal barbecue, you will need to add 12 ignited charcoal briquettes (or the equivalent in hardwood charcoal) to the fire along with the chips every 45 minutes to maintain the grill temperature. (Light the charcoal in a chimney starter on a fire-safe surface, or use a small portable grill or hibachi.)
For either barbecue, do not add more wood chips after the 1 1/2-hour point, as too much smoke will give the ribs a bitter flavor.
Once the ribs are tender, begin brushing them lightly with the barbecue sauce every few minutes or so, allowing the sauce to set before applying the next coat. Continue brushing the ribs with the sauce, turning occasionally, for about 30 minutes, or until the meat has shrunk from the ends of the bones. Transfer the ribs to a carving board and let rest for about 5 minutes.
To serve: Using a large sharp knife, cut the racks into individual ribs. Transfer to a large bowl and toss with enough of the remaining warm barbecue sauce to coat. Arrange the ribs on a platter and serve with the remaining sauce on the side.
Make-Ahead: The ribs can marinate up to 24 hours, covered and refrigerated.