That reminds me, a few folks have been using very sharp flush mouth trim as-is. For example, folks using the Dillon trimmer or the WFT just leaving the cut square without chamfering and deburring. I find the sharp inside edge scrapes copper off bullets, but if you simply burnish the inside of the mouth, that stops, and the crimping die will burnish and blunt the outside of the case mouth. Most commercial cases, with exceptions like Lapua, are not chamfered coming out of the box, but rather are just dulled by tumbling and the commercial makers load them that way.
A burnishing tool recommended by Bart B. is an EZ-Out. I took one and polished the outside smooth, just to minimize friction removal of brass. It has a left-hand spiral thread, so when you chuck it in a drill it does an nice, non-grabbing burnishing of the inside edge. I even use is on chamfered case mouths to prevent copper scraping. Works just fine and doesn't mar the brass the way a smooth tapered cone can when spinning.