About 30 minutes before smoking, make the dry rub. Combine all ingredients in a small bowl; mix well.
Spread both sides of ribs with yellow mustard and sprinkle with dry rub. Let stand at room temperature for 30 minutes.
Heat charcoal or gas grill for indirect cooking at 250 degrees F. Place the ribs, meaty side up, over a drip pan and cook for 4 to 6 hours until very tender. Spritz ribs occasionally with water or apple juice using a spray bottle. Add about 12 coals to a charcoal grill every 45 minutes or so to maintain the heat.