I recently did this at work to a chauffeurs car.. He was out there buffing his headlamps with a cloth while waiting for his client to come out. I grabbed some of the plastic polish I had in my trunk(friend needed it) and let him have it and told him to let the other drivers use it too if they have a problem.. He found me later next week and told me how his boss was amazed at how his car had the best headlights out of them all. he thought the driver went and bought new ones!