there are lots of ways to get a good fuel/water-proof finish. Is the boat made of wood? a lot depends on the type of finish you're looking for and what the hull is made of. if you want the best looking finish, automotive primers, base coats, and clear coats look fantastic when done right. but there's a weight penalty with multiple coats. West Systems Epoxy #105 resin and #206 hardener come highly recommended as a sealer for the inside and outside of wood hulls. i use the #205 hardener, but i'd recommend going with the #206 for the longer pot life. you can get it at marine/boat supply stores or on the web through mail-order at several places but you'll pay for shipping. here's 2 sources i know of-
http://www.superiorbalsa.com/ and
http://www.cstsales.com
you'll need access to equipment necessary to spray the paints, and automotive paints are nasty stuff to breathe. there are easier and cheaper ways to get a decent paint job, but now that i've used the 2 part/2 stage auto paints and clears, i'll never use anything else again. not sure if you want to go through the extra work and cost involved. i've gone the cheaper way using 2-part hobby epoxy type paints as well and when done right, they'll work ok. some guys here have used different brands of the spraycan type "fuel proof" paints and have had luck with them. the spraycan paints i've tried just haven't resisted high nitro fuel very well around the fuel tank and engine areas.
someone recommended the PPG 2021 automotive clearcoat on an earlier post and I have to say that he was right, that stuff is awesome. and the available autopaint colors are limited to the imagination.
if you like airbrushing graphics, or would like small amounts of exotic (expensive) paints like house of color, here are some sources i've come across-
http://www.airheadairbrush.com/House%20of%20Kolor.htm and
http://www.innate.com/home.htm
do a search on this forum and there is a lot of info regarding finishing. you can also use
http://www.google.com/ to search the web. important- whichever method you choose to go with, if you are using more than one product make sure that they are compatible with each other. have fun!