You pour a small amount of grit on a plate, add enough water to act as a lubricant anf then hone until its time to go onto the next grit or the grit has become degraded and doesn't remove much material. You don't need a lot - less than an egg-cup full or thereabouts. Like most things, you have to try it out and draw your own conclusions.

You can start off using 80 grit, but that is very coarse and it takes a while to get the scratches out, so I use something like 140grit - even on hard stones like CFS and LIs. The finishing is not done with grit, as it 'rounds off' the sides. If you have a couple of grits in diamond plate, say 400, 600 or 1200, then use these to remove any rounding.

Barbers Hones are best left as they are IMO. The top surface once lapped often gives out altogether, or changes the nature of the hone. Barber Hones that have pits where the original material has plucked out are undergoing the first stages of breakdown anyway, and will last longer if you do not lap them.

Regards,
Neil