I would tend to go for what I am using on my paper tiger. It is made by wattyl and is called 'timber preserver' . it is a two part epoxy coating and is quite thin to start with and you generally thin it 50% for first coat, 25% for second and straight for final.. it is amazing stuff and penetrates right into the grain of the wood and will repel water unlike if you got a scratch in it say with just normal highbuild / primer. and the beauty of it is once you have finished with it the topcoat goes straight onto it.