I use my cheaper DB Escher 4 inch stone as a slurry stone for my other eschers/thuri's. There is a guy on the bay selling synthetic/natural nagura's that range from 1k to 12k. I bought his 12k, it is natural and keeps me from wearing down my escher four inch. I also would not use my coti slurry as others have mentioned, same with the dmt. Basically you need a pretty hard stone to produce your slurry on that G escher. I feel that you could also get away with using a cheaper koma nagura also available on the bay for less even still.