rejuvenate faded paint?

Very light wet sanding by a pro than a nice buff should do the trick. I think!

When the hood is wet does the paint look normal? If so then you can just polish it to bring it back. Go to an automotive paint supply (like where a bodyshop would go) and show them your hood. Then they'll select the best "cut" polish to bring the hood back. More than likely they'll have 3M stuff which I would recommend. You can then use a machine or do it by hand (I did mine by hand for a smaller area and it worked great), and you'll have the hood looking like new in no time. EDIT: I shouldn't say that, it actually takes a while by hand

If its only water spots, then use a clay bar to remove them.
Hope I helped

I agree that buffing compound should get it out.. if not then you will probably have to resort to wetsanding then rebuffing afterwards. Water spots like that wont come up with just washing.. ive had them befor. Try a cleaner/wax first if you have some.