Today I finally got to use the norton flattening stone I bought from howard.
O-M-G

This is just so much better than messing about with sandpaper.
My stones are much flatter than they used to be.

I can now easily do one-handed honing. I used to use 2 hands. I know this sounds really crazy and I can't explain it, but I have no problems anymore, honing with one hand. The stones feel totally different now.
I also get a much better result in much less time.
This is the best 25$ I've ever spent on razor related stuff.

question: on the paper it says that if you use them a lot, the flattening stone itself needs to be flattened. Has anybody ever had to do this?