Cook the ribs bone side down, over indirect heat, with the grill lid closed, for 1-1/2 to 2 hours, or until the meat just starts to shrink back from the ends of the bones. (Don’t overcook; meat should shrink back less than 1/4 inch.) To ensure even cooking, set an oven thermometer next to the ribs, also over indirect heat. During the last 30 minutes of cooking, baste the ribs with the sauce mixture every 10 minutes. Set the rib racks on a baking sheet and cover with foil; let them rest for 10 to 20 minutes, then slice and serve.