Sounds like you're off to a good start. Every stone I have is different. I'm not sure I could tell any of them apart by the shaving edge, but I could sure tell which is which by the feel of the lapping. What aoki calls 8.8 should be plenty fine for razors, especially if the hardness is there to get clear water. I can't remember if I've ever had a hard shoubu, it is only the softer ones that I put tools on (lv 4 from takeshi kuroda). Their fracture lines are like what you'd expect if you took a carbide or diamond scribe and scraped it on glass. Not only does the scratch occur, but it fractures at the edge and becomes much larger than you'd expect. But that will never happen with a razor, and there was otherwise nothing wrong with those stones other than their softness. Every stone I have that I can finish a razor with, I can figure out a way to do it and get a good edge every time or very close. Some of the great stones pretty much, you rub a razor on them just about any way you want and they make a quality edge.

I have given up on nagura other than tomonagura on the harder stones (not because there's anything wrong with it, it just takes longer). I work a new razor on a washita only for the bevel set and then the final stone. That's it. It's fast and I have better consistency that way because the washita doesn't leave many surprises on the edge (the grooves are relatively wide and shallow) to clean up. I'm sure a nagura progression is fun, but in my experience, washita stones make better prefinishers. There's something about them. They are like the good medium natural stone that the mines in japan just can't quite seem to cough up. Responsive to technique, and either fast or relatively fine (depending on how you choose to use them) but gentle on the edge.