Yep. I'll just add I DO sort by headstamp, and I just have ziplock bags with REM WIN and all that on them..
I used to. And, I do still work new loads up (generally) only in Winchester brass for 9mm and .380 Auto.
But, once I have the load finalized, I load it up in my "grab bag" of brass - 2-4 of each head stamp of significant quantity in my stash (about 170 cases, total). I run all of that through the pistol, and call it good if there were no issues. From then on, the load is run in bulk on my Dillon 550B, with mixed brass. I still inspect everything, but I don't bother sorting.
In contrast, as F. Guffey is always bringing up, I go to great lengths to sort, prep, and track my rifle brass. But for semi-auto handgun cartridges, 9mm especially, I haven't found even sorting by headstamp to make any real difference.