'marine' grade varnish is more or less permanent - the wood will decay before the finish degrades.

after that, two or three good coats of any poly-clear is your best solution - the craft paints (ceramacoat is the best of the bunch, IMO) are 'half' UV stable, so they do fade with time, but not as fast as paints in general used to.

brushing will let you put a heavier coat on surfaces that will get the most wear/sun/abuse.