I've shot hundreds of rounds made from cases with media in the flash holes and it doesn't make a damn bit of difference as far as I can tell.
I used some of those 30-06 cases i tumbled while deprimed for a few matches and my scores were consistent with other scores with factory ammo and other handloads that were confirmed to not have any blockages.
Shoot 'em and don't waste your time picking it out. The media will come out when you fire the round...you can trust me on that
Half of this shit with reloading is voodoo, I swear to it. All these queers out there 'neck turning' and confirming the liquid volume of their cases need to stop making youtube videos and get to the range.
@mac1911 even got me to think twice about cleaning my brass!
I've never cleaned, reamed, or uniformed a primer pocket in the few years I've been reloading. (i DO swage military brass, of course)
I've found that the best thing you can do to improve accuracy...is reload as many cartridges as possible and get yo' ass to the range and shoot them!