Maybe I can shed a little light on the situation. I, too, live in Florida (Titusville) and have been in and around bodywork for over 40 years...

Metal Prep is an acid. Its purpose is to dissolve microscopic rust and etch the surface of NEW metal so that primer & paint will stick to it. If you have ground or sanded the metal it is already etched. You won't need to use Metal Prep unless visible rust has formed. (This would be a golden cast to the bare metal. If the rust is actually red-brown and you can feel it, you will have to sand it off again.) While your work area is still in bare metal, wipe it with Conversion Coating. This is a liquid that is rich in Zinc. The Zinc will attach itself to the steel surface and protect against rust. It is only one molecule thick, however, and will not pretect the metal indefinitely. It must be followed immediately with primer. If you are working outside you need a waterproof epoxy primer.

If you are using Metal Prep, it goes on first and is dried off with clean rags or paper towel. Next comes the Conversion Coating. Excess is wiped off again and follow as soon as possible with primer or primer-sealer.

Hope this helps...