Definately go with Marine Paint!
Don't ask me how I know

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I have had excellent luck with West Marine brand paint. Both for Fiberglass and Aluminum. Follow the directions, if it calls for an expensive primer, fork out the dough, it pays in the long run.
I have painted a couple of boats and have rolled and brushed the paint on, and have had excellent results. Most of the Marine paints that I used were self leveling paints, so; no ugly lines.
Good luck!