ZenNMotion

I've polished up many older cranksets to look better than new. But I don't think you'll have much luck with clearcoat paint, it will look great for a few weeks then not so much. You could try a commercial powdercoater to put a more durable clear on, it would be harder than paint. Polishing is easy, though messy and time consuming. Lye-based oven cleaner (Easy Off) sprayed liberally and left for an hour will remove the aluminum anodized coating, and will turn the component a mottled ugly industrial gray-black, that's Aluminum Oxide. Don't leave the oven cleaner on too long or you will start to pit the surface. Obviously use rubber gloves and safety goggles, you don't want that crap on your skin. Rinse it well in water, and clean up the soaking container well, lye is no joke despite the fact that you can buy it at Safeway. Then, Mother's Aluminum polish (auto parts store) or any kind of metal polish to clean it up. If it's scratched or dinged up, use a green Scotchbrite pad followed by fine wet sandpaper. Finally, a cotton buffer wheel on an electric drill or dremel tool with some jeweler's rouge wax on the wheel. The more you work at it the more mirror-like it gets. Repolishing later is pretty easy, just a little Mother's polish on a rag to buff it up. The surface should stay polished for awhile depending on how much rain etc you see- salt spray will dull it quickly if you ride near the beach.