Just want to update that I got my K&M tool a few days ago. I put it on the drill (low speed) and the thing is awesome. Using the hand tool I would spin it in there for 3 to 5 seconds per piece and while cleaner than before, it wasn't exactly spotless.
With the K&M tool I place it inside the primer pocket, low speed for a few turns and walla! Nice and shiny inside.
