About one hour before smoking, coat both sides of ribs with a little vegetable oil and sprinkle with barbecue seasoning rub. Set aside at room temperature for 1 hour.
Heat charcoal or gas grill for indirect cooking at 230 to 250 degrees F. Add drained wood chips, if using.
Place the ribs, meaty side down, over a drip pan and cook for 2 hours. Add about 12 coals to a charcoal grill every 45 minutes or so to maintain the heat.
Remove ribs from grill. Double-wrap each rack in heavy-duty aluminum foil. Return wrapped ribs to the grill and cook for 1 1/2 to 3 hours more over indirect heat, until very tender. Add more coals as needed to maintain temperature for a charcoal grill.
Meanwhile, make the sauce. Combine all ingredients in small saucepan. Bring to a boil over medium-high heat; reduce heat and simmer 15 minutes, stirring frequently.
Remove ribs from grill and unwrap. Place ribs over direct heat on grill and brush with Kansas City-style barbecue sauce. Cook for about 5 minutes until the sauce is set. Turn ribs and repeat with more sauce.