Preheat the smoker to 225°Fahrenheit.
Remove the membrane from the back of the ribs by sliding a butter knife under the membrane and pulling it off with a paper towel.
In a small bowl, combine the brown sugar, paprika, salt, pepper, garlic powder, onion powder,
cayenne pepper, dried thyme, and mustard powder. Mix well to ensure all ingredients are evenly distributed.
Generously apply the seasoning mix to both sides of the ribs. Use your hands to rub the mixture into the meat, covering all areas thoroughly.
Place the ribs in the smoker, bone-side down, and smoke for 3 hours, maintaining a consistent temperature.
After 3 hours, remove the ribs from the smoker and wrap them tightly in heavy-duty aluminum foil. Before sealing the foil, pour 1/4 cup of apple juice into each foil packet.
Return the wrapped ribs to the smoker and cook for an additional 2 hours.
After 2 hours, remove the ribs from the foil and place them back in the smoker. Brush the ribs generously with the BBQ sauce on both sides.
Return the ribs to the smoker and cook for an additional hour, uncovered, to let the sauce set and caramelize slightly and the ribs are tender.
Remove the ribs from the smoker and let them rest for 10-15 minutes before cutting and serving.