H17,
That sucks! It would be helpful to know what type of bottom paint was used. First, I have to tell you that that stuff is toxic, so keep it out of your lungs, off of your skin, out of the water, off of your lawn etc.
The boat yard that I used to work at would pressure wash the big chunks off then apply Peelstrip:
http://www.dumondchemicals.com/
Once you get the majority of the paint of, you'll notice that some of the cuprous oxide has leeched into the gelcoat. Nothing can take care of that other than sanding my friend. Depending on how bad it is you might be able to get rid of it by wetsanding, but you'll probably have to dig in with some 80 on a flatboard. I'd have to see it.
I would advise against any type of paint as it will not last well past 1 beaching. Gelcoat is the way to go. Get the paint off first and post some pix. Chances are, if you're sort of careful with the removal, you'll be able to buff the remaining gelcoat out and it will be as good as new. You may have to patch a few spots, but its way easier than spraying the whole bottom.
What color is your boat?
Good Luck!