If you have access to something like a diamond lapping plate, that'll get you started faster, with the caveat that you have to work with the edge trailing or you'll just be making new chips. You can't "scrub" with those, or even the really coarse stones of other types, with harder steels. I mean, you can, but it isn't going to end well imo. I sure as hell wouldn't with a knife I cared about.

Fwiw, with something in the 400 grit range (or equivalent), it shouldn't take thousands of passes, just hundreds. Well, assuming the steel isn't freakishly hard. But I've never seen one like that that went over maybe 65 Rockwell. Ish. Obviously, if you've only got a single 1 stone, which is perfectly reasonable for 99% of what most people need, it'll take thousands lol.

Just to kinda babble on about something I enjoy as a tangent (so feel free to just ignore the rest lol), I tend to favor oil stones, particularly for rehab jobs like that, and leave the water stones more for polishing when I need/want something that can do fancy push cuts. It's what I reach for first with this kind of task. The coarser aluminium oxide stones can actually do a solid job on the Japanese steels, and they take less lapping over time by virtue of wearing slower.

There's the argument that water stones are exposing fresh grit faster, and thus the lower grit water stones can remove metal faster as well. However, I find that the faster wear of the stone shows up in a wonky bevel that then needs more time correcting. Plus, if you don't go with something crazy low grit (say, under 200 for this application) you can actually scrub as long as you're careful. I managed to do solid jobs on similar steel that way with no new chips.

Anyway, like I said, I'm just geeking here, not trying to get you to do any of that. It's really the kind of job that you either do because you enjoy it, do because someone is paying you, or you find someone else to do it :)