I've done a lot of these repairs. A good oil based house paint will last a long time and is way cheaper and easier than fiberglass resin. Just make sure to seal any drilled holes with paintable silicone caulking. The method described by skeetbum is more work and more expense, but it will last for an exponentially longer time. I agree with the others that RAKA is the place to get resin and hardener. It's far superior to the polyester stuff at the auto parts or home improvement store. Don't use salt treated wood. If sunlight can get to it, you'll need to cover the epoxy with latex paint. Even the epoxies that claim they have UV stabilizers don't last too long in the sun (in my experience).