I have been using corn cob media specifically made and treated for cleaning/polishing brass. I tumble my brass before I size it and then for a little while after I size it to remove sizing lube. This second tumbling always results in many primer flash holes being filled with media. Is there a size of media that can be purchased that will not clog the flash hole? What size am I looking for? If I purchase untreated media, anybody have a "home-brew" cleaning/polishing additive?

I just toss my finished rounds into my corncob media to remove the lube. I don't buy into the tumbler breaking down the powder idea, especially for just the short enough time to remove the lube.

As far as treating the media, I've heard of many people using regular auto polish. Never tried it myself though....

I tumble my brass before depriming. Tumbling doesn't seem to clean the primer pockets very well anyway.

Course walnut shells work pretty well, but occasionally you sdtill get a granual into the flash hole. I tumble before I deprime so it just doesn't matter. Using non treated cob or shells & add Dillon case polish or Nufinish car polsih works well.

If you lead a good life, in Heaven they have corn cob media that doesn't clog but here on earth, a Bic Stik works about as well as anything I've tried.
Since I lightly lube the inside neck of my bottle neck cases before resizing, I like to tumble them before I prime, etc to get the lube out of the neck. And it gets the worst of the crud out of the primer pocket.

Try adding a few cap fulls of 3M Professional Swirl removing polish , Finesse-it 2.( Part # 05928 or 051131 ). It contains NO silicones , wax or other garbage . I add it to my Dillon large tumbler with Walnut media . I even have a mixture of both Cob and Walnut which I add 2-3 cap fulls of that stuff to clean nasty cases when need be !. Pour the cap fulls around on the media don't just pour in one place . It doesn't take a lot !.

Shoot Straight Know Your Target . ...

Whether I use corn cob or walnut shells I get media in the flash hole from time to time... I simply have my universal decap die in hand and when I find some media in the flash hole I just drop the case in the decap die... The media is gone and I'm off to the next case...

Ken....