Seconded!
But only after you've done all the chassis painting you need/want to as it's a swine to clean it all off later.
I'd recommend using POR15 paint (like Hammerite on steroids - you can get it from Frosts) on the most vunerable bits of the chassis and then waxoyl after that.
Then there's always the 'Kleentect' option...
It is a job you're thinking about having a go at yourself?