Combine first 6 ingredients in a large bowl, stirring until salt and sugar dissolve. Pour salt mixture into a large zip-top plastic bag. Add ice and pork; seal. Refrigerate for 3 hours, turning the bag occasionally.
Soak wood chips in water 1 hour. Drain well.
Prepare grill for indirect grilling, heating one side to medium-high and leaving one side with no heat.
Place wood chips on hot coals. Remove pork from bag; discard brine. Pat pork dry with paper towels. Sprinkle 1/8 teaspoon salt over pork. Rub 8 teaspoons Pepper-Garlic Spice Rub evenly over both sides of pork. Place pork on grill rack coated with cooking spray over medium-high heat; grill 2 minutes on each side. Place pork on unheated side of grill; grill 3 minutes on each side or until done. Remove from heat. Let stand 5 minutes before serving.