This is a great tip. Based on my empty-the-medicine-chest-and-travel-size samples testing, all the following did a good job with no scratches added*:
- Tom's of Maine "Natural Tartar Control & Whitening"
- Arm & Hammer "Complete Care - Intense Freshening + Whitening"
- Colgate "Cavity Protection - Great Regular Flavor"
*My test sample was an old pair of plastic glasses... don't know if this is representative of the plastic on our favorite cars. When I tried the same pastes on an old CD there was some fine hazing from all 3 (least from the Tom's), so I guess it depends upon how soft the plastic is or what type of plastic.
As a comparison, I tried the same thing with the Porsche "Polyglass Window Cleaner" and also the 3M "Finish Restorer". These two products seemed to cause no hazing on either the glasses or the CD, and the 3M product even appeared to be able to remove the hazing left by the other products from the CD.