Prepare the ribs: Place a rack of ribs meat side down on a baking sheet. Remove the thin, papery membrane from the back of the rack: Insert a slender implement, such as a butter knife, under it on one of the middle bones. Using a dishcloth for a secure grip, peel off the membrane. Repeat with the remaining rack
Make the rub: Combine all of the ingredients in a small bowl and mix well.
Make the Shanghai barbecue sauce: In a medium nonreactive saucepan, combine the hoisin sauce, rice wine, soy sauce, sugar, ketchup, vinegar, garlic, ginger and minced scallions. Cook over low heat, stirring frequently, until the sauce thickens, about 5 minutes.
Generously sprinkle the ribs on both sides with the rub, using about 1 tablespoon per side and rubbing it onto the meat. (Any leftover rub will keep for several weeks in a sealed jar away from heat and light.) Cover the ribs with plastic wrap and refrigerate them while you set up the grill.
Set up a charcoal grill for indirect grilling, with the coals piled on each side. When the fire is moderately hot, set a large drip pan in the center of the grill. Oil the grill grate. Place the ribs bone side down in the center of the grate, over the drip pan and away from the heat. Toss half of the wood chips on each mound of coals. Cover the grill and cook the ribs for about 2 hours, until they are well browned, cooked through and tender enough to pull apart with your fingers. When the ribs are done, the meat will have shrunk back from the ends of the bones by about 1/4 inch.
Just before serving, brush the ribs on both sides with the Shanghai barbecue sauce and move them directly over the coals. Grill until the sauce is sizzling, 1 to 3 minutes per side; watch carefully so the sauce doesn't burn. Transfer the ribs to a large platter or cutting board and let rest for a few minutes. Cut into 1- or 2-rib pieces and transfer to a platter. Garnish with the chopped scallion greens and serve, passing the remaining barbecue sauce on the side.
Adapted from Raichlen on Ribs by Steven Raichlen (Workman, 2006).