Sprinkle brisket (both sides) generously with celery seed, garlic salt, and onion salt. Sprinkle both sides with liquid smoke (1 ounce per pound of meat). Wrap in foil and seal well. Place in refrigerator overnight to marinate. Bake at 300 degrees approximately 1 hour per pound of meat. Pour off liquid at end of baking time. Slice thin; pour barbecue sauce over and brown sugar. Bake another 20 minutes at 350 degrees. Excellent!