Note he seared the meat and then cooked it with the fat side up. He said this is very important. He smoked the meat for about 35 minutes and then added the horseradish sauce. Continued to smoke it until a meat thermometer registers at 165 degrees. During the smoking/cooking process he added more sauce to each side of the loin. Flip occasionally and add more sauce. Serve with a nice salad or your favorite veggie.