How to restore old, scratched plates I have some old lego plates that are quite scratched. They look rather dull compared to the newer pieces in my collection. Is there any way to restore (even partially) the shiny look between the studs? 

I'd heard that using toothpaste can help smooth out transparent pieces, so I tried putting toothpaste on the plate. However, it seemed like it would be insane to try to rub the paste manually between all the studs... so I used a nylon brush to brush the plate. That didn't seem to help much, but didn't make it any worse. Would it have worked if I'd manually rubbed the paste in? Is there a faster way of doing that?
Brasso (yes, the metal polish) works better than toothpaste in this case. It is a bit more grainy so works faster but doesn't damage the parts. It does take some work though that may or may not make sense depending on the rarity of the elements. 

And yes, with either toothpaste or Brasso, you actually have to vigorously rub the surface to buff it up. It might be easier and cheaper just to replace the worn parts with new ones if they really bother you.

LEGO getting scratched up a bit is normal. In most colors you won't even notice it, but there are certain colors where scratches are more visible&nbsp;— with black being the worst. So it actually helps to store black parts stuck together to prevent rubbing against each other in storage.