Place chicken in a greased 5- or 6-qt. slow cooker; sprinkle with garlic powder and top with onion. Combine the barbecue sauce, salad dressing, brown sugar, vinegar, Worcestershire sauce and, if desired, liquid smoke; pour over chicken., Cover and cook on low for 6-8 hours or until chicken is tender., When cool enough to handle, remove chicken from bones; discard bones and onion. Skim fat from cooking juices. , Shred meat with 2 forks and return to slow cooker; heat through. Serve with potatoes, 3/4 cup in each. Top with blue cheese and green onions if desired.