I'm not sure what the emphasis of your original query is, so here goes the shotgun answer:
1. Putting standard copper based anti-fouling
on your stainless steel
prop shaft will not cause damage to the shaft.
2. It is difficult to get anti-fouling to stick to smooth s/s, so it is likely to come off fairly quickly. If one puts epoxy
based hi-build primer on the shaft it MAY help with this problem. Since the shaft is fairly small in diameter, the surface speeds are not huge, and since it is in front of the prop the water flow is not terribly turbulant, so there is some hope. Use of a hard paint rather than an ablative one also helps.
As of this writing our bottom paint
is nearly 5 months old, and we have travelled almost 2000 miles since application. The shaft is still painted and still un-fouled.
Propellors are a different case entirely. Their high tip speeds, induced turbulance and worse yet cavitation will rapidly remove paints. We're trying Prop Speed for the first time this year, and so far it has kept the prop clean, even in high-fouling areas. I had a look yesterday and it had some fine "fuzz" on it, but it wiped off with my bare hand. We had just spent 17 days in the Trinity inlet (Cairns) where the unpainted bottom of our rib
had acquired a lot of barnies and some soft growth.
Hope this helps with your decision.
Jim and Ann s/v Insatiable II lying Michaelmas Cay, Qld, Oz