Undercoating or Rust Proofing for Winter

Hey all, do you or do you not get your car coated for winter seasons? I live in a northern climate with a lot of road salt in winter, and I’ve heard so many differing opinions on this subject, so here are my questions:

- Do you get rust proofing done?
- Do you have a preferred brand/process/coating
- Has it been successful in preventing or slowing rust?
- Is it necessary, in your opinion?
- How much did it cost?

Any advice would be appreciated, happy driving out there - boost season is coming soon!