Here is solution for hard brass, my Lee trimmer will not cut it, so I grabbed a piece of brass, turned it for a close fit, threaded the end to fit the Lee handle, bored it for a 3/8ths end mill, cross drilled and tapped for a set screw, the 2 flute end mill will trim hard brass.
Very east to transfer skills, I know a couple of good 'smiths and they both said easyer to make a Smith out of a tool maker then teach a Smith to be a tool maker.....