1. Preheat an indirect barbecue with a drip pan and fruitwood (preferably apple), a ceramic cooker with deflector plate and fruitwood (preferably apple), or a charcoal or gas grill with a box or packet of fruitwood (preferably apple) to 250°F.
2. Using a paring knife, make a straight cut between each of the bones, starting from the top of the rack where the bones are exposed and cutting down to just before the top of the meat. Combine the seasoning blend ingredients. Combine the mustard moisturizer ingredients. Stir the seasoning blend into the moisturizer and then rub on all sides of the meat. Using your hands or a brush, evenly, but lightly, coat the racks with canola oil. Insert a remote thermometer into the center of one of the racks.
3. Place the racks, fat side down, in the cooker. Cook to desired doneness; for rare (120°F) about 30 minutes, for medium rare (125°F) about 35 minutes, for medium (130°F) about 40 minutes, for medium well (140°F) about 50 minutes, and well-done (150°F) about 1 hour.
4. Meanwhile, place all of the dressing ingredients in a jar with a tight-fitting lid and shake to combine.
5. Remove the racks from the cooker and let rest for 15 minutes. At this point, the racks can be dressed and served (skip the next step of charring), they can be charred, or they can rest for up to 1 hour before charring. If charring, remove the deflector plate of the ceramic cooker or preheat a well-oiled charcoal or gas grill to medium-high.
6. To char the racks, place the racks on the grate, fat side down, and cook without moving them, with the lid open, until well marked and lightly charred, about 2 minutes. Flip, and with the lid open, repeat on the second side, grilling for about 2 minutes.
7. Give the dressing a quick shake to reincorporate any ingredients that may have settled. Drizzle some of the dressing on a cutting board. Top with the racks and let rest for 10 minutes.
8. Cut the lamb into individual chops and dredge in the dressing on the board. Sprinkle with fleur de sel and serve.