I usually put a good number of bullets in the container, but never quite got this much coverage, so what I tried different this time was to use put only a "hand full" of bullets in the shake-bake container at a time. Literally as many bullets I can grab with a hand. This of course resulted in fewer bullets being coated at a time than any prior attempts.
I then did circular shaking for about 40-50 seconds, with a little up-down, but mostly high-speed circular, and that resulted in the most coverage I have had to date. Due to the smaller groups I had to do more batches, but the batches were fairly consistent in terms of coverage, so for now I will keep trying this method/variation to my PC routine. I have to remember Ian's advice to tap them to get some of the clumps off next time.