the lower link rising.sun just posted is exactly right. Look at the before and after pics, that is definitely what you can expect. But if you go with the paint, it won't be as durable, and will be a lower gloss.
If you have damage that isn't quite so bad as in the pics on that link, and its something that amounts to oxidation (dusty dry rubber), and 303 type stuff is out, try a regular car wax. We would need to reapply monthly, but that was in continuous exposure to the hot Caribbean sun. The inland marine company sells something
for that, but I'd go to Walmart instead, just heed their no petrol products warning.