I'm not a real painter but have painted boats and done touch-up jobs. These days, two part polyurethane from an automotive or boat supply place is a good and very durable material available in all colors of the rainbow.

I have not seen anyone recommend the Preval painting system. These are used frequently in yacht repair for small jobs, which is what painting a bike frame would be. I've seen a real painter spraying Awlgrip do a perfect mirror finish on a 55 foot custom sailboat. http://shop.preval.com/collections/p...preval-sprayer