dinnermint makes an excellent point that I too have followed.

I NEVER use a diamond plate for raising slurry on a coticule, only another piece of coticule as a slurry stone. Why? Coticules are made from larger garnet crystals (think glass) and sharp shards of diamond will easily fragment those garnets, leaving sharp pieces in the slurry or sticking out of the substrate. Gently using a cotigura (small coticule hone meant for raising a slurry) will be more likely to release the garnets from the substrate without harm and it is their round soccer ball shape that makes them work so well. I have no proof of course, but it seems to work for me, so that's my theory.

I do use a diamond plate to initially flatten a coticule (I did it once, maybe 15 years ago) and after that I have cleaned the surface with a cotigura and only use that for cleaning, raising a slurry or refreshing the surface. My coticule is rather hard and does not seem to auto slurry like many of them do, so it has not dished on me. But even if it did, it would have a long way to go based on the old hones we occasionally find that were used until they looked like a saddle.

Regards

Christian