I was under the impression to do it properly water based paints need a 2 pack clear topcoat applied after, which is definatly NOT a home diy job.
Doesn't have to be 2-pack no, but I was advised (by a paintshop) that the water-based they use needs covering with something. I use GIP Gloss, it's a 1 pack ready mixed, just needs a bit of buffing to get a shine.
Any solid colour that's water based will dry to a waterproof finish. Synthetic paints have been around for over 30 years, it's just that they have got better now because they are the mainstay of the refinishing industry rather than a cheap alternative.
My advice, seek the advice of the paint suppliers when you buy. Buy a decent quality gun and take your time.