I haven't had much luck getting paint to stick to my props. Usually
only takes a couple of times out for it all to come off. I'm sure
there are systems out there that will work but you could always try
Boudreaux's Butt Paste. It works well for keeping the prop clean in
between uses. Of course someone has to go under to apply it, but it is
a cheap alternative.

As for staying underwater long enough to do this, I just spliced 50' of
air compressor hose between my primary and safe secondary regulators.
I can leave my tank on the back of the boat and dive under. If
anything goes wrong, I'm only 6' under water. I know the air
compressor hose is technically unsafe to breathe out of, but I've been
doing it for years with no ill effects.

Later,
Dan Schiro
M/V Sea Ranch