Here's an idea:
¼ cup salt
2 tablespoons olive oil
1 tablespoon pepper
Dissolve salt in 2 quarts water in large container. Submerge pork loin in brine, cover, and refrigerate for 1 to 1 ½ hours. Remove pork from brine and pat dry with paper towels. Rub pork loin with oil and coat with pepper. Let sit at room temperature for 1 hour.
Clean and oil cooking grate. Place pork loin on hot side of grill, fat side up, and cook until well browned on all sides turning as needed. Use smoke wood for flavor.
Move loin to cool side of grill, positioning roast parallel with and as close as possible to heat. Cover (position lid vent over roast) and cook for 20 minutes.
Rotate roast 180 degrees, cover, and continue to cook until center of meat registers 140 degrees.
Transfer roast to carving board, tent loosely with foil, and let rest for 15 minutes. Remove twine, cut roast into ½-inch-thick slices, and serve.
-- The Editors at America's Test Kitchen (2012-10-12). The Science of Good Cooking: Master 50 Simple Concepts to Enjoy a Lifetime of Success in the Kitchen (Cook's Illustrated Cookbooks). Boston Common Press. Kindle Edition.