Although you'll still have to do the fairing and block sanding that Frizz describes, why even spend all that time and effort on gel coat, which is porous, will quickly oxidize anyway and require frequent maintenance?! I'd use Signature Finish paint, which doesn't require any primer and will work fine below the waterline, unlike most other urethane paints like Awlgrip or Awlcraft. It's intended for DIY use, is easy to roll & tip and repair, and can be buffed to eliminate any orange peel. I used it on my
bottom painting project 5 years ago and it's still holding up great. Island Trader used something called Insignia which is also supposed to be good for below the water line and is probably better if you want to spray it. I read the All At Sea article on the new paint forum member Shine is selling at a good discount, and it also sounds good, although I don't know if it will hold up underwater. All the paints are probably a bit more expensive than gel coat, but if you count your time and labor as worth anything, I think any of the paints would be far superior, longer lasting and less maintenance than gel coat!