I'm curious as to the community's experience with what I'm calling "cross-border" slurry - i.e. using a non-native rub stone on a native base stone to create a slurry. So for example: using a Thuringian rub stone on a jnat, or a nagura on a coticule or even on a synthetic stone, or vice-versa for any of these or other combinations. (I'm not talking about using different nagura on jnats in a progression.) Does anyone do this regularly? Any interesting observations? Apologies if this has already been discussed elsewhere (or if it's otherwise a ridiculous enquiry. . . ).