One good product would be some stuff called Ever Brite. It is a clear coating that can be brushed or sprayed on, is durable and easy to touch up. I'm using it on my various completed assemblies while they sit in the hangar and wait for the rest of the airplane to be built to protect them from surface corrosion.
On the Rebel Builder chat group there are many Murphy Rebel and Super Rebel (Moose) builders who use it as a coating on their floats because it is durable and easy to apply and touch up and is quite tough once cured. Polish the airplane to where you want it, apply Ever Brite and it will stay like that indefinitely.
For more information see
http://everbrite.net.
Works for me, of course, your mileage may vary.
Steve