When I lived in NY (516) I used to get a hose from inside the house every other week and rinse off the undercarage when the car was warm. Before winter I would get under the car for an hour or two to wipe and oil things down. I would do the same at the end of winter too, when I was sure they were done with the salt. Not many people want to go though all that.
As far as paint goes rinse off as often as possible when its salty and wash when you have a good stretch of weather.
I don't miss the salt!!!