Using a sharp knife, make 1/4-inch-deep slashes in the rib meat between the bones, without cutting through. Spread all but 1 tablespoon of the spice rub over the ribs and into the slashes and let stand for 5 minutes.
Meanwhile, in a small saucepan, combine the hoisin sauce, ketchup and the remaining 1 tablespoon of spice rub and bring to a boil. Cook for 1 minute, then transfer to a bowl.
Light a grill. Lightly brush the ribs with oil and grill over a moderately high fire, turning frequently, until the ribs are sizzling and cooked through, about 25 minutes. Brush the ribs with half of the hoisin glaze and grill for 2 minutes longer. Transfer the ribs to a cutting board and cut in between the bones. Serve the ribs with the remaining hoisin glaze on the side.