CHICKEN: Heat gas grill to medium-high or charcoal grill to medium-hot coals. Sprinkle chicken on all sides with seasoned salt and paprika.
When grill is ready, place chicken on grill grate. Cook, turning once, for 18 minutes, or until thigh registers 180 degrees on an instant-read thermometer.
BBQ SAUCE: Heat oil in a medium-size saucepan over medium heat. Add onion and cook 5 minutes. Stir in vinegar, ketchup, brown sugar and mustard. Bring to a boil, then reduce heat and simmer 5 minutes.
Remove chicken from grill and allow to cool slightly. With two forks or your hands, shred meat from bones. Add shredded chicken to sauce and heat through. Divide chicken evenly among sandwich buns, a heaping 1/3 cup on each. Serve with coleslaw and potato chips.
COLESLAW: In a large bowl, stir together all ingredients until blended. Refrigerate 1 hour before serving, so all the flavors marry.