Preheat oven to 120C. Mix rub ingredients (Mexican seasoning through to smoked paprika) well in a small bowl until combined. Place ribs meat-side down on a foil lined roasting dish. Remove silver skin from the back of the rack and prick meat several times with the tip of a knife. Generously coat rack with rub. With rib rack meat-side down, fold foil around it to create a tight seal. Bake in preheated oven until tender and cooked through, about 2 hours. Remove and cool 15 minutes. Increase oven temperature to 175C then open foil, package before draining and discard any accumulated juices and fat. Brush BBQ sauce on all sides of the rack.
Place rack meat-side up and return to oven, leaving foil open. Bake for 10 minutes, remove from oven, and brush another layer of barbeque sauce on meat-side only. Repeat baking and brushing with sauce 4 more times, for a total of 50 minutes baking time. If desired, cut rack into individual ribs and serve with more sauce.