Place each chicken tender between 2 sheets of heavy-duty plastic wrap; pound to 1/4-inch thickness using a meat mallet or rolling pin. Cut each tender in half crosswise.
Combine hot sauce, butter, and ketchup in a medium bowl; reserve 3 tablespoons mixture, and set aside. Add chicken to remaining mixture in bowl; toss well. Thread 1 piece of chicken onto each of 18 (6-inch) skewers. Sprinkle evenly with salt.
Cover a large baking sheet with foil, and coat with cooking spray. Place skewers on prepared pan, and broil 3 minutes on each side or until done. Brush with reserved 3 tablespoons hot sauce mixture. Serve with celery and dressing.
Note: If using wooden skewers, soak them in water 30 minutes before broiling.