As I said I knock the primers out. Sure there is media in the flash hole. Probably 90% have it. Easily picked out but more importantly it gives me yet another chance to exam my brass as I pick the kernel though.I would think that if you are using a vibrating tumbler with brass that has been de-primed that you will have a lot of cases with media stuck in the flash holes… and in my experience, a lot of dust inside and out side of the cases.
Sizing with a die that has it’s de-priming pin in it will get the stuck bits out of the flash holes but now you have debris on and in you press.
I am bumping & neck sizing then setting neck tension with a mandrel so I don’t use a de-priming pin in the die along with pulling the neck sizing ball through the neck.
With SS pin wet cleaning my primer pockets are clean, brass is factory fresh but now fire formed to my chamber. In the end, what ever works for you is what is best… {:~)
As far as dust goes I really don’t know as the media I’ve been using isn’t leaving any ‘dust’. Then I clean each flash hole with a primer pocket cleaner . Not really a pain but another close look at the brass.
If you noticed so far the brass has never entered the die yet, so there’s really no debris.
Here’s what I noticed. Seems everyone has their own method and system. I’d never say mine was better. What I will say is that it has worked successfully for me and my rifles. I’m only interested in my group size. Yeah I tried some jewelry type spotless brass but it did nothing for reducing group size. Ever. Do I think my method is superior to others? Nope. Inferior? Nope. I shoot some really small groups with my methods in my rifles with me shooting.