Dimetcote is one of the best corrosion inhibiting primers on the market. But... it requires specific surface preparation. Products like Ameron Sealer and other penetrating epoxy products are much better for marginally prepared surfaces seen outside of shipyards and newbuilds.
Products like Ospho and Corroseal both contain phosphoric acid which makes used difficult on states such as California.
To remove rust stains look for caustic degreasers containing chemicals like sodium metasilicate. Walmart's Super Clean in the purple jug is a good example. This stuff works well and does not etch paint. I also believe it is overlooked by the Vessel General Permit so you can still use it in California.