Pretty sure he is talking about Permatex Rust Treatment spray. From what I can tell by having used all three recently it is the exact same as Loctite Extend Rust Neutralizer and Rust-Oleum Rust Reformer. All of the instructions say that that they are rust converters and may actually cause rust if used on unrusted metal. I've always used as per the instructions, scuffed after full drying period and topcoated with no bad results to speak of. But it has always been small parts or small areas, and watch for overspray as it will discolor other paint. I am sure there is probably a better product for covering large rusty areas, or combination converter/encapsulators.

For preventing initial rust formation on bare metal I've heard good things about Rust Prevention Magic, but have yet to open the can that I have. IIRC it is wax based so probably not something you want to try to paint over.

If you are going to paint and protect bar metal, I'm thinking its hard to beat careful metal prep and catalyzed epoxy primer and sealer.

Good Luck