How long to make slurry with the hard slurry stones?

Like ovidiucotiga, I have hard jnats and with a similarly hard tomo it may well take 3 minutes of rubbing to get a light slurry, but the results are usually very good.

As far as I can tell, when a jnat seller says the stone is hard and takes 'advanced honing skills', they mean you have to be patient raising slurry and don't push too hard. After all, once you have the slurry nothing else is different. And when you're buying a high-end thin Japanese kitchen knife they'll sometimes say that you need 'advanced knife skills'. As best I can tell, this means not trying to turn the knife clockwise or counterclockwise with the edge in contact with the cutting board.

Neither skill is really very advanced but is just part of using specialized tools.

Cheers, Steve