Twice I think I bought one size up from the small kit and had too much both times. My props are a bit bigger too. I think they are 27 or 28.
I’ll tell you this, read the instructions. The stuff doesn’t work if you screw it up, and that’s easy to do. Read the curing speed/steps carefully. I would not do it in warm weather, it kicks off FAST. Their recommendation to work with a partner is spot on. I do mine alone. Once it went terrible. Once it went well. The last time it was a little too warm. I kept up with the product curing, but barely, and I was cursing the whole way. My top coat was a little uneven in places as I was running out of time an going berserk speed. Remember, the product doesn’t care if you are not prepared, or tried really hard. Either you meet the curing speed perfectly or you might as well scrape it all and start over. It’s not a forgiving product.
I’d do props and shafts. For rudders, I’d instead apply interlux 2000 barrier coat. There is a bit of prep and effort with the 2000, but comparatively easy to apply a few coats. Then you can just bottom paint the rudders and lose the zincs on them too. Much easier future for just a little extra effort today.
Anyway, good product, but I’d also say most amateurs will screw it up and think it doesn’t work. I’m 2 for 3. Also if you get a yard to do it (good idea) do NOT take the lower bid. Yards screw it up frequently to of the b squad is called in to meet a lower cost.