Place milk in a deep bowl, add pepper flakes and rosemary. Season meat with black and cayenne peppers. Place meat in the bowl, add milk as needed to cover. Let marinate 3-4 hours. Remove meat from marinade, discard marinade. Pat the meat dry. Re-season the meat, if desired, with black and red peppers. Add salt to taste, if desired. Brush meat with olive oil to reduce sticking, and grill over hot coals, or over medium heat in a gas grill for about 10 minutes each side, brushing with oil again when turning.