Place each rack of ribs on a sheet of heavy-duty (or double layer) foil large enough to wrap around ribs. Sprinkle with salt and wrap in foil, making an air tight seal. Transfer to a rimmed baking sheet and roast 1 hr 30 min.
Heat grill to medium high. Lightly brush ribs with some barbecue sauce, remove foil and grill, turning once, until grill-marked and golden brown, 8 to 10 min. Generously brush with remaining sauce, slice and serve.
Notes
You can bake several racks at a time and be prepared for a crowd.