Preparation Mix salt, brown sugar, black pepper, granulated garlic, paprika, and cayenne in a small bowl. Place spareribs on a rimmed baking sheet; pat dry with paper towels. Using a paring knife, remove silver skin from underside. (It should come off in a single sheet; start to separate it with the tip of your knife, then pull away with your hand. Removing the silver skin allows the dry rub and barbecue sauce to penetrate the meat; if you purchased ribs from a butcher, the silver skin may have already been removed.) Sprinkle dry rub all over ribs, patting to adhere. Using your hands, spread a thin layer of barbecue sauce all over ribs. Wrap in foil and chill at least 2 hours and up to 1 day. Prepare a grill for medium indirect heat (for a charcoal grill, bank coals on one side of grill; for a gas grill, leave one or two burners off); oil grate. Strive to maintain a grill temperature between 280°F and 300°F. Place foil-wrapped ribs, bone side up, on grate over indirect heat. Cover and grill 30 minutes. Uncover grill and turn ribs over. Cover and grill until a meat thermometer inserted into the thickest part of ribs registers 145°F–160°F (peel back foil as needed to check), 20–30 minutes. Unwrap ribs and brush on both sides with more barbecue sauce. Grill, bone side up, uncovered, until sauce darkens and meat very tender and falling off the bones, 10–12 minutes. Using large tongs, carefully transfer ribs to a cutting board. Let rest 5–7 minutes before cutting between bones into individual ribs. Serve ribs with remaining barbecue sauce on the side.