Fire up your charcoal grill to 225°F (107°C). Make sure it is set up for 2-zone indirect cooking, with the coals sat to one side.
Place 1-2 chunks of apple smoking wood on the coals as it warms up. Set up a grill thermometer on the indirect side to gauge ambient cooking temperature.
While your grill warms up, trim the pork tenderloin. Remove any silverskin or excess fat. Rinse with cold water and pat dry with paper towels.
In a small bowl, combine dry rub ingredients. Use a fork to remove or crush any lumps that form.
Apply dry rub across the pork surface, covering all sides. Work the rub into any folds or crevices on the pork’s surface.
Place the pork tenderloin on your grill’s grates on the indirect side. Close the lid. Smoke until the pork tenderloin's internal temperature is 135-140°F (57-60°C), approximately 45-60 minutes.
With a basting brush, lightly baste the pork tenderloin in BBQ sauce. Cover all sides evenly.
Place pork tenderloin back on grill grates. Smoke until internal temperature hits 145°F (63°C).
Remove pork tenderloin from smoker and place on chopping board. Slice into ½-inch thick medallions and serve immediately.