I live in an area where our cars are bathed in salt 1/2 the year. I usually don’t do any maintenance other than oil,air filter, brakes, and tires because rust causes too many issues once a car is ~12 years old anyway. Been getting interested in cars and maintenance and want to do what I can to make our cars last (especially the 2015 Toyota). Is there anything that isn’t a gimmick can be done to combat rust once it’s had years to get a grip? I know rinsing off is a good idea…but time and a place to do it in the winter is hard to find.

Bonus points for the 70’s vibe label, I’ll go for it when the weather breaks. I appreciate it.
@Chucktobias introduced me to Fluid Film. They put it in spray cans, it's around $11.99. I used it on my '99 Ranger in a couple spots where I was concerned about rust progression. I applied it in November, and I can still tell it's there. The frame of my truck still repels water where I spayed it.
For application on large areas, an air-powered spray gun loaded from a gallon pail of the stuff is the ticket. I spray the entire underside of my winter vehicles each fall.
Fluid Film, NHOU, are just 2 that come to mind, and there are other sprays available. But see what's being used and effective in your area.
Yes there are systems that you can apply to the vehicle that will help.