Cleaning stained plastics and refinishing

I did a logic board and screen swap yesterday as the case was damaged and heavily stained.

I decided to go all mad professor and us the damaged case to test some cleaning products/techniques and used a pot of oven cleaner that we had lying around. This is basically a very fine grit paste used for cleaning metals etc which worked fine and didnt leave any real heavy abrasion marks. What it did do is obviously remove a fine layer which gives the plastic a nice shine.

Im wondering if anyone knows of a way/product/silver bullet that can restore the shine back to the plastic as this could give an old, tired case a new lease of life and make the Macbooks I'm refurbing look that little bit better presentation wise.