I tried to powder coat some Lee 405 HB that I had cut the stud off. I used HF red powder. I shook that tub for 20 minute, top popped open twice, but the powder would not go into the grooves. So I picked them up by the nose and dragged them through the powder. That mostly filled the grooves, probably too much.
First bake left a good number of bare spots. Attempt to re-coat rendered a sloppy mess.