First use a paper towel to dry off the pork tenderloin. Then, using a large sharp knife and a cutting board, remove any fat remaining on the pork. You may be able to pull it off with your hands. If not, cut it off with the knife.
Next remove the silverskin (connective tissue) on the tenderloin. You will need to poke the tip of the knife into the tenderloin just under one end of the silverskin, then gently and gradually move your knife back and forth as you slide it down underneath the silverskin to remove it from the rest of the meat. It will need to be removed in multiple sections - if you try and remove it all at once you will cut away a large portion of the meat itself.
Once the silverskin is removed, measure out the kosher salt with a measuring spoon and sprinkle it all over the meat, spreading it around with your fingers until the meat is equally covered. Place the meat on a plate and in the fridge, uncovered, for 8 hours.
Take the tenderloin out of the fridge after the 8 hours is up and 30 minutes before you put it on the grill to let it warm slightly.
Set your wood pellet grill to 250F and let it come up in temperature. Use measuring spoons to measure out the spices in a small bowl and stir to combine. Sprinkle the mixture onto all sides of the pork, rubbing it in with your hands.
Once the grill reaches 250F, place the pork tenderloin on the grill and, if you have it, insert a meat probe and set the temperature of the probe to 130F. Cook the pork until it reaches an internal temperature of around 130F, then slather the bbq sauce on with a brush. Continue cooking the tenderloin until the internal temperature reaches 145F. Remove from the grill, let rest for 10-15 minutes, then carve and serve!