for your slurry to be predominantly from the rubber you'd want the rubber to be softer, other wise it'll be a mix, or predominantly coticule.

the BBW may be softer than the coticule, meaning you can work with predominantly BBW slurry, which while typically slower, sets a better bevel then coti slurry anyways.

feel free to mix slurries from different types of stone. it's not a common idea, and lots of folks dont, but it still works. i've wondered what could be done with a large c12k and an array of slurry stones only.