What 3K stone and Welsh slate are you using?

Your best bet is to drop back to the 3K. 1K if you have it. Magnification will also help immensely, if you don't already have a 30x loupe.

It can be done on a finisher. I've done it. But if you have a lower grit stone, why spend all the extra time trying to make it happen with what should be your final stone? Maybe if you're just messing around to see what works and what doesn't, but the most expedient way to get where you need to be is to ensure that the bevel is set before moving beyond the 3K.