I had my doors and under hood done with the "dealer rustproofing", you know, the yellowish paint-like grease stuff......personal,y I'm gonna spray some fluid film in the doors and spray the underside myself with a oil/trans/steering fluid kinda mix. Did my Wrangler with it last year and it's still there, although it doesn't see winter use, lol.

Poor results with Krown, and really it's a lot of money at the end of the day. I'd think the thing to do imo is touchless car wash with underspray at least once a week in the winter. Probably cheaper than Krown, plus the car is clean.