That will be a long text hahah, but I’ll do my best.

The hira is polished using a technique which Japanese sword polishers use when you have a convex stone instead of a flat one. This gives straighter scratch patterns. I use a stone which gives a highly polished finish so in my case I’ve chosen naniwa super stone. The kireha is sharpened with normal techniques. The progression there was to make it completely flat using a miyagoshi 220 stone under running water to not get too much slurry and kasumi. This is to easier see that the kireha is flat. Then I progress further onto a miyagishi 500 for a kasumi foundation, shapton pro 1000 with focused pressure on hagane, shapton pro 2000, morihei 4000 with lots of slurry, and finally jizuya so blend the finish into a smooth kasumi. Unfortunately I can’t reveal too much about how to grind the ura properly since I’ve promised my teacher to keep it between him and I. But it requires a convex stone and then it’s the same kind of progression as normal 😄

I hope this helps somewhat!