I would think that the easiest way for the manufacturers to go about this, is to let model clubs (who already know a thing or two about how to set up a contest) do the show, and they in turn will sponsor them. This, in turn with a good healthy dose of Harry's "much to gain, little to lose" mantra, may be just the ticket.
Also, if anyone thinks there is a perfect formula for promotion in the 21st century, well I doubt it. Nothing ventured, nothing gained.