I'm not familiar with that particular brand, but I have lapped quite a few barber hones.

I start at 325, or 120 if the hone is a harder one. Sometimes I stop at 325, sometimes I finish as fine as 1,000 wet/dry. Chamfer the edges. I like to flatten the 2 long and narrower sides too, for possible use on warped razors.

Slurry isn't normally used with a barber hone (some are pretty hard). If yours is soft enough you can try it with slurry and see what happens. Water or lather is often used. The only way to know what grit you have is to try it, unless a member who owns one can help.