I'm not a huge fan of 3-2-1 ribs,(I prefer a little more tug), but my wife loves them. St. Louis style, dry-brined the night before and coated with Memphis Dust before I put 'em on.
I smeared a little bacon grease, brown sugar, butter, Memphis dust and a splash of apple juice when I foiled them. Average temp was 240 on the SnS with KBB, and a few chunks of pecan & hickory.
The last hour of the cook, I put a very, very light coating of Rib Rack BBQ sauce, (cuz that's what Mrs. Skinsfan likes
), and the last 10 minutes I open all of the vents.
I prefer traditionally cooked ribs, but 3-2-1 ribs does offer the advantage of knowing exactly when they're going to take for them to be done, which is a rare occurrence when smoking meat.