I antifoul my bronze rudders and stainless trim tabs, but don't bother with the shafts, as for some reason they don't seem to get too fouled, maybe because they're in tunnels.
I don't antifoul my stainless shaft or rudder, or the bronze prop. Nothing on them that doesn't easily clean off during the annual lift out/clean/hull antifoul.
I should point out that we're in the med, where barnacles can have quite an effect during the season. We didn't a/f the rudders when we were based in UK, though I don't see a great problem with doing them.