Undercoating for Winter?

[R01k]

I've heard conflicting opinions about undercoating against winter road salt. Some say that it actually contributes to hidden rust due to the humidity keeping effect of the thick coating.

In a few weeks we'll start the snowy period here in central NY and in my town roads will stay salt-spread for almost 6 months, so I'll definitely need some rust protection, even if it's just car wash under-spray.

Some advice?

[MetroMPG]

I'd avoid barrier type undercoating and use a light oil type of spray that "creeps" into cracks & crevices. (Also drips on the driveway/garage floor for a couple of days, so take that into consideration.)

Do you have commercial rustproofing services available in your area?

There are 2 or 3 different companies to choose from in eastern Ontario that will treat the entire car for about $150, which includes drilled access holes to spray the insides of rockers, doors & wheel arches as well as the underbody. Or you can get just the underbody done.

EDIT: you can also buy aerosol cans, eg: