True the onshore winds will be carrying salt if your'e near the ocean, but not everywhere in Hawaii has surf breaking - waves tumbling in gives off huge amounts of droplets that evaporate down to brine that keeps attracting moisture from the air and corrodes like crazy. That's where plenty of fresh water washing w/ fine plastic bristle boating deck brush and rinsing (daily) would be required...
If your trailer was shipped in an enlosed space you are ahead of the game, between that and dock holding areas in a marine environment the salt will have already compromised the vulnerable spots already.
Do drop in on the local small plane airport scene and ask around how they protect the airframes & fuselage from salt. Voice of experience there probably won't lead you wrong.
Aside from maintaining the shell I'd be tempted to spot coat exposed frame areas, axles & mounting hardware, and any other iron or steel showing corrosion with a phosphate rust-protection coating like this
http://tinyurl.com/k9uly . Beware the hardware store varieties have a plastic coat base that can trap moisture underneath it, still rusting like crazy but have shiny black finish hiding the damage - moisture wicks in from edges and builds up layers of rust underneath like a pastry shell.