i'm don't have a ton of experience, but the couple of knives i've polished so far i did entirely on stones, and using that method, the first thing you will discover is whether the grind has high and low spots. probably start with a medium grit and you will find out pretty quickly if there are spots where a flat stone just can't reach. from there decide whether you want to go to the effort of dropping down to a course grit stone to flatten the bevel, or if you want to switch to sandpaper. i believe you can keep a crisper shinogi if you stick with nice flat stones, but it will be a lot more work.