OK; Rust-proofing/Undercoating?

I was in the rustproofing business a couple lifetimes ago. At the time there were 2 main rustproofers, Dura-coat and Ziebart. Dura-coat had a zinc chromite solution that was the best on the market. Supposedly the zinc would bond to the metal via the chromite solution. The Ziebart was easy to get customers away from as they used a wax based solution. It usually took over an hour to clean the zeibart cars because of the necessary overspray. The Dura-coat if applied correctly had practically no overspray. I lived in Minnesota then, Now I live in AZ and have not given the subject a 2nd thought until now