I should also mention that I have never used that slurry method I mentioned with the Nortons before. Again, no expert but I believe that they are aggressive enough already and I don't know how well that would work with them. I actually only do that on the giant gray block with limited strokes per solution and not with much weight on the blade.
I was mainly mentioning that to say be aware and maybe scrub them lightly with a nylon brush to remove it.