I just avoid water like the plague. I'm of the opinion that washing after every use is more harmful than good, unless you have a way to dry it all over very fast. There are too many pockets that will hold the water. My mower deck has never been washed. It's now in it's 17th season and no rust of any significance. It is stored indoors, and I simply scrape off the main crust each spring when I sharpen the blades. It isn't necessary nor worth it to be so meticulous about it.
Treat my tractor the same way. I've washed it maybe 4 times in the 16+ years I've owned it. When you wipe off the dust, the finish still looks almost new, and no rust anywhere.
I did use slip plate the first season. But, quickly came to realize that it was a waste of time and money. Don't know about the bedliner option. Probably good if you get it applied such that it will not trap water.
I do, however, use fluid film on all nonpainted (irridited steel) parts, applied from a spray can about twice a year. Those aren't rusting either.