Trim fat from brisket. Cut the brisket, if necessary, to fit in a 3-1/2- to 4-quart crockery cooker. Add water, vinegar, Worcestershire sauce, and cumin or chili powder. Cover and cook on low-heat setting for 10 to 12 hours or on high-heat setting for 4 to 5 hours.
About 1 hour before serving, remove the meat from the cooker. Discard cooking liquid. Using two forks to pull, shred meat and return it to the cooker. Stir in barbecue sauce. Cover and cook on the high-heat setting for 30 to 45 minutes or until heated through. Serve atop split Kaiser rolls or hamburger buns with pickles and onion, if desired. Makes 12 to 16 sandwiches.