Dry the ribs using paper towel. Remove the membrane from the curved side of the ribs.
Apply the mustard to the entire rack. Pat the seasoning evenly onto both sided.
Let the rack sit with the rub for 10-30 minutes while the smoker is coming to correct temperature. Place ribs onto the hot grill and close the lid. Spritz with water or apple juice every 20-30 minutes and turn.
Once the internal temperature reaches 204-207 degrees, remove the ribs from the smoker and place them onto a sheet of tin foil. Add in 3-4 pats of butter and about 1/4 cup of your favorite bbq sauce. Seal up and place back onto the smoker and grill another 10 minutes.
Remove and let rest for 10 minutes. For the final step: Take the ribs out of the foil and place them back onto the smoker grill. Baste with bbq sauce, just until they become tacky (approximately 15 minutes). Serve with your favorite sides!