Mix liquid smoke, garlic salt, onion salt, celery salt and Worcestershire sauce. Sprinkle brisket with pepper. Cover both sides of meat with sauce in a baking dish. Cover tightly with foil and place in refrigerator overnight.
The next day, bake (covered) at 300° F for 5 hours. Add barbecue sauce after 4 hours and leave uncovered from then on.
Slice and serve.Servings: 10 to 12