No. You don't have to use slurry. There was a gentleman on here that used to say: "Use a lower grit". It just takes longer, that's all. 8k is still 8k, 4k is still 4k, etc... Natural stones do not need slurry either, For example, The Charnley Forest hone. (Yes, I know it's used with oil) That's just one. Even Coticules and BBW's can be used without slurry, as a finisher. Some Cotis are so soft, they generate their own slurry. Lot's of guys buy them thinking, "I only need one hone" and quickly find out, that's not really true. It really depends on what your trying to do. Slurry will increase the speed at which a stone removes metal, nothing more. It cannot change the grit of a stone.