You can dilute boat soap, but I doubt that the results will impress you much. Outdoor Windex and the automotive equivilant (Mr. Clean?) are both examples of strong detergents that reduce or eliminate the need for a brush and dry without spotting, but that's at the expensive of ANY wax that you may have had when you started out.
If you find a bottle of ANYTHING on a store shelf that claims to be a spray-on wax, it's lying. The best those products can do is leave an oily film behind that could be a safety issue on a boat deck.
As far as caveats go, the biggies are blowing away bedding and caulk. Keep the spray away from ALL deck fitting and windows. It won't do much on smooth gelcoat either, but it might be useful for digging out ground-in dirt from your non-skid areas.