What can I use on my fiberglass tub and shower surround that will buff.....?

it back to a glossy shine? I figure there has to be some kind of compound I can use along with a buffer to bring it back from the dead. It is dull and hard water spots and soap scum adhere to it like a magnet, making it look dirty. I waxed it with marine wax last week and it looked great for a little while but it's dulling already. Any ideas??