My 12 week lab puppy loves to chew on our leather furnitre. We have many toys and try to detur him from biting with introducing a toy when he bites the leather furniture and also tried frozen wash cloths. We use a firm NO! But almost seems to get more playful and thinks it's a game. Can I use bitter apple on my leather furniture? I'm afraid it might stain. Is there any other product I can use? HELP!