I wouldn't bother nowadays mate. Modern galvanised chassis and body panels provide better protection than any spray on or 'electronic protection' systems ever will. The main rust potential is from crash damage where the galvanising is damaged and where you cut/drill etc panels or chassis for modifications. Just make sure you prime and paint these areas well afterwards.
Everything metal made will corode over time, That's why it's smart to delay the time it takes before nature takes it back. I use this: http://www.fluid-film.com. I do not say it's the best, but cheap IF u can do this your self. Google and find out