I use "Turtle wax Ice polish", It is real easy to work with and you can put it on about anything (plastic, rubber,vinyl) it can be applied in direct sunlight and on hot surfaces.
I found this stuff a while back and it is really about the best thing I have ever used for protection and shine. It is safe to use on...well...anything. Glass, plexiglass, plastic, metal, paint, chrome, vinyl...anything. After a good soap and water wash I go over all of the plastic parts with this. One of the great things is that it keeps bugs and road tar from sticking...they just wipe right off with the next wash easy as pie.
Another trick I learned from a veteran dirt racer a while back is to use WD-40 on the metal parts (don't put it on plastic!). It cleans off even the toughest of baked on road tar and protects high heat areas quite well. I use it on all of the exhaust and high heat engine areas. It also helps keep the chain grease from sticking to the left lip of my back rim.