Again, I haven't done this before, but this is what I would do.
Get bowl/dish/something with a flat bottom. Put ~2mm of hydrogen peroxide (H2O2) and put the nozzle straight down on the bottom of whatever bowl/dish is being used. Only the grill has to be in the H2O2, not the whole nozzle. And don't worry about damaging the driver as the driver is inside the larger part of the earpiece. Just always keep the nozzle facing downwards. Anyways, keep the nozzle in the H2O2 for a few minutes then rinse it with water (you can use a similar bowl/dish but with a few mm of water instead). Then put it back in the H2O2 for a few minutes again and rinse. Keep doing that a few times to get it fully clean. You'll then want to let it dry for a little while, I'd give it 1-2 days.