Set up a smoker as directed in How to Cook Ribs on a Smoker (following).
Meanwhile, on bony side of each rack of ribs, loosen membrane at one end with a table knife and pull off membrane with a paper towel. Set ribs on 2 rimmed baking sheets and coat all over with oil. Sprinkle generously all over with rub, patting it in.
Smoke ribs at 250° to 275° until meat shrinks about 1/2 in. from ends of bones and a rack will bend easily, 2 1/2 to 3 1/2 hours; if some racks finish before others, remove and cover (see next step).
Transfer ribs to clean rimmed baking sheets and wrap snugly with foil. Stack pans, wrap snugly with a couple of layers of thick towels, and let meat rest 1 to 3 hours. (This makes it more tender. You can also wrap racks in foil and keep warm in a cooler lined with beach towels.)
Heat a gas or charcoal grill to medium-low (300° to 325°). Unwrap ribs. Brush one side of ribs with glaze and grill glazed side up, covered, about 3 minutes. Turn, brush with more glaze, and grill until ribs are browned and sizzling, 2 to 3 minutes total. Set ribs on boards, cut apart, and sprinkle with parsley.
* St. Louis-style ribs have been trimmed of the chewy skirt and cartilage. Buy them at well-stocked grocery stores, or trim yourself: On the bony side, trim the flap of meat from the center, flush with the bones. Then cut the rack lengthwise between the 4- to 5-in.-wide rib section and the chewy skirt. Save scraps for soup.
How to Cook Ribs on a Smoker
"Now that I have a $25,000 grill at work, I want easy at home," says Quinn Hatfield. For smoking ribs he likes both of the following models, as each is designed to maintain a steady low temperature with almost zero effort. (But do check on food every 45 minutes or so.) You'll need regular, not competition-style, charcoal. For the Weber smoker, you'll also need 4 fist-size chunks of applewood.
Pit Barrel Cooker. Inside the drum-shaped cooker ($299; pitbarrel.com), meat cooks directly over coals and the drippings produce smoke to flavor the meat. Quinn Hatfield adds no additional wood with this smoker.
Adjust bottom vent for your elevation (see manufacturer's instructions); this keeps smoker at the right temperature without the need for a gauge.
Fill charcoal basket level with regular charcoal briquets. Transfer 40 briquets to a charcoal chimney and ignite in a fireproof spot. Set charcoal basket in bottom of smoker, pour ignited charcoal on top, and spread evenly.
Set smoker rods at top of smoker (for ribs, don't use grill racks). Securely place one hook two bones down into center of thicker end of each slab of ribs (the end with bones that go all the way across).
Hang ribs from rods in smoker, leaving space between slabs. Meat should sit at least a few in. above coals; if not, move hooks in ribs to three bones down. Set lid in place.
Weber Smokey Mountain Cooker. Available in several sizes (the largest, at 22 in., holds the most ribs), this smoker uses water to help keep foods moist. Quinn Hatfield adds a few chunks of fruit wood to enhance the smoky flavor.
Take the lid section, tall middle section, and bottom section apart. Completely open all vents in bottom section and lid.
Set firegrate in bottom section, top with charcoal ring, and fill ring halfway with regular charcoal briquets. Distribute 4 fist-size chunks applewood in charcoal. In a fireproof spot, ignite an additional full chimney of charcoal (for a 22-in. smoker) or half-chimney (for an 18-in. smoker) and let burn until dotted with gray ash. Pour over charcoal in smoker and spread evenly.
Put water pan in middle smoker section and set middle section in place. Quickly (before pan gets hot) fill water pan three-quarters full.
Close bottom vents halfway. Set bottom cooking rack in place over water pan and arrange half of ribs on rack. Set top rack in place and add remaining ribs. Cover with lid. As ribs cook, adjust vents if needed to keep temperature at 250° to 275°, always leaving top vent and at least 1 of bottom vents partially open so fire doesn't go out.