I am fine tuning Hi-Tek coating and have been perplexed by the occasional little globs of coating on random bullets. After a period of revisiting all the usual steps I was still scratching my head.
Then by happenstance I noticed some bare spots on the inside of the "swirl" container. Turns out that the acetone from the fresh mix was sloughing off the dried-on mix from prior sessions. That semi-moistened coating was loosening from the container and transferring to some bullets.
I then tried enlisting some clean plastic. Bingo! Results are now as expected. So my method going forward will include using a new vessel for swirling each session.