Place tenderloins in a 5-qt. slow cooker coated with cooking spray; pour 3/4 cup salad dressing over pork, turning to coat. Cook, covered, on low 4-5 hours or until meat is tender.
Remove pork; cool slightly. Shred meat into bite-size pieces; return to slow cooker. Stir in brown sugar and remaining salad dressing. Cook, covered, 30-45 minutes longer or until heated through.
Combine slaw ingredients. Serve pork on buns with slaw and, if desired, mayonnaise.