Not really any 'best' method, only what's 'best' for you Depending on the level of 'ducky-do' at your sailing site, some soapy water ought'a work just fine. Wipping it down, on site, is good. Then wash it at home. Windex in a spray bottle seems to work fine for me (lazy).
Cleaning for an exhibit? Beats me, never built anything that would stand a chance anyway, so a little dirt wouldn't hurt at all.