Set up your grill to cook indirect (push charcoal to one side and cook meat on the other side) or use an offset smoker for indirect cooking so the indirect side is 300F.
While the grill and smoker are warming up, place pork tenderloins onto baking sheet. Remove the membrane by placing a thin sharp knife under the membrane and cut parallel to the tenderloin.
Generously sprinkle spice rub(s) onto the pork tenderloin. Ideally you can barely see the meat through. Flip the pork tenderloin over and generously sprinkle the other side of the tenderloin so that it is seasoned on all side.
Place pork tenderloin on indirect side of grill or offset smoker for 20 on indirect grill or 30 minutes on offset smoker. This cooked the tenderloins to 110F. The bark should begin to set (the spice rub is adhering to the meat so that it doesn’t rub off when you rub your finger against the surface). You can also rotate the tenderloins or move around on the grill if your coals are getting hot and burning the rub.
Flip pork over on the grill or offset smoker.
Using an instant read thermometer, at the doneness of your choice by probing in the middle of the length of the tenderloin, remove the pork tenderloin off the grill or smoker and place onto a baking sheet or pan, loosely cover the pork loin with aluminum foil and allow to rest. This can vary between 20 -60 minutes.
US Department of Agriculture recommends cooking to 145F with at least a 3 minute rest. https://www.usda.gov/media/blog/2022/10/03/cooking-meat-it-done-yet#:~:text=Cook%20raw%20beef%2C%20pork%2C%20lamb,minutes%20before%20cutting%20or%20consuming 145F -150F medium rare150F-155F medium155F-160F medium-well160F well Rest pork tenderloin under a loose piece of tin foil for at least 15 minutes or until ready to serve.
For sandwiches: With a sharp knife, slice pork tenderloin 1/8”/ 3 mm thin to make a pile of pork tenderloin on a burger bun or slice or bread. Top with barbecue sauce and enjoy!
Personal Note: On an offset smoker, at 300F, I cooked the pork tenderloins on a Yoder Wichita offset smoker, top shelf by the exhaust for 30 minutes, flipped the tenderloins and cooked an additional 50 minutes to 135F.