I'm cleaning the cylinder head of my brick which blew a headgasket at cylinder #1 passenger side water gasket; it leaked coolant only outside the engine. There's a lot of rust on the deck of the cylinder head and around each water jacket. The gasket sprayer spray, carburetor cleaner, brake fluid, and scraping with a plastic scraper do not remove the rust. Any tips?

Also, I inherited this car from a New England owner who obviously didn't keep up maintenance (there are other problems too numerous to mention here). What do you think of adding a rust preventing chemical (eg Prestone Anti-Rust) to the coolant at this point?