We have about 30 boats in our club at our marina on the upper Chesapeake Bay where the waters are mostly fresh to slightly brackish depending on rainfall, and location. A few years ago we conducted a test of prop protection. About 12 boats participated. They were to use whatever they preferred and the results were monitored prior to launch and after haul-out. A variety of methods were used from bottom paint, expensive prop paint, high zinc primer, etc. The winner hands down was the 90% zinc primer. You can pay $20+ in a marine store or about $8 in a home store. Same stuff, more or less.
Application consists of removing all foreign material from prop and hub. Polish surface to remove any corrosion. A light sanding may help to provide some "tooth" to the surface. Immediately before spraying, clean the surface with mineral spirits or similar. That's it. Maybe 30 min.