We had no success with paint on our propeller last time around.
This time we are trying straight up Lanolin. (It is an ingredient of some diaper rash creams and the main ingredient of the Lanocote product previously mentioned)
We applied it two months ago while we were on the hard.
So far so good. There is absolutely no growth on the propeller, while the bottom paint already sports a green fuzz. We just recently put in 75 hours of motoring over a two week period so it will be interesting to see if that has worn it off....
We are in the PNW, so cold water.....I am not sure how an in the water application would go. It might be hard to spread.
I think it is worth a try though. Theres nothing to lose
Lanolin is cheap, can be purchased at the pharmacy, non toxic and renewable product that will not harm anything....including your prop and shaft.
And if it does not work, you can use it to keep your skin soft.