Ribs: Pat dry ribs. Grab and remove the membrane using a paper towel from the back of the ribs removing it completely. Drizzle with olive oil.
Dry Rub: In a small bowl, whisk together brown sugar, salt, chipotle pepper, paprika, chili powder, cumin, lemon pepper, granulated garlic, oregano, black pepper, crushed red pepper flakes and onion powder. Rub the ribs on all sides with the rub.
Spray the inside of a 6 quart oval slow cooker or similar size crock pot with cooking spray. (You can also use a slow cooker liner) Arrange 1 rack of ribs along the wall of the slow cooker insert.
Arrange the second rack of ribs on the interior of the slow cooker.
In a medium bowl, whisk together the Dr Pepper and liquid smoke and carefully drizzle over the ribs. Lock the lid in place.
Cook on low for 7-8 hours or until fork tender and easily pierced with a butter knife. The ribs will become very tender, so, handle carefully. Remove to a pan and cool uncovered. (You can chill them for several minutes to speed up the process, if cooking immediately)
After cooling, cover with plastic wrap and chill, if making in advance.
To Broil: Move the oven rack to the highest position and set on broil. Spritz a baking sheet liberally with cooking spray. Brush one side of the ribs with bbq sauce. Broil for approximately 4-5 minutes per side or until charred. Repeat with the other side. Rest uncovered for 5-10 minutes before slicing and serving with extra sauce.
To Grill: Preheat the grill to medium. Liberally oil the grates. Brush one side of the ribs with bbq sauce and grill until charred, approximately 4-6 minutes per side. Repeat on the opposite side. Rest uncovered for 5-10 minutes before serving with extra sauce.