Pour liquid smoke over brisket and rub on all sides. Sprinkle with celery salt, garlic salt, onion salt and meat tenderizer. Place brisket in refrigerator, covered with foil. Leave set over night. Drain liquid smoke. When ready to bake, sprinkle both sides of beef with salt and pepper. Add a little worshestershire sauce. Bake covered for 5 hours at 275° F.
Uncover meat and pour 1/2 bottle barbeque sauce over it. Bake 1 hour uncovered. Remove meat - remove fat from juices. Add flour to thicken juice. Add remaining barbeque sauce to taste. Pour over sliced meat. Cool first, before slicing. Then heat to serve.Servings: 6