In small bowl, stir together dry mustard, paprika, oregano, seasoned salt, sugar and pepper.
Remove ribs from packaging; rinse in cool water. Pat dry with paper towels. Cut rack in thirds.
Season ribs with 1/4 cup of the dry rub, pressing on with your hands. Pour beer or broth and 1 1/2 cups water into slow cooker. Stack ribs in cooker and cover. Slow cook on LOW for 9 hours.
Heat gas grill to medium-high or coals in charcoal grill to medium hot. Place remaining rub, brown sugar, vinegar and ketchup in a small saucepan. Bring to a boil over high heat. Reduce heat to medium and simmer 5 minutes, stirring frequently.
Carefully remove ribs from slow cooker. Baste with sauce. Grill ribs 6 minutes, turning after 3 minutes.