Preheat oven to 300°. Combine garlic salt, paprika and pepper; rub over roast. Place in an ovenproof Dutch oven; add soda. Bake, covered, until pork is tender, 2 to 2-1/4 hours., Remove roast; shred with 2 forks. Skim fat from cooking juices. Return 1 cup juices to Dutch oven. Add ketchup, steak sauce, liquid smoke, brown sugar and vinegar. Bring to a boil; cook for 5 minutes. Return meat to pan; heat through. Adjust with additional cooking juices as desired. Serve on hamburger buns.