I clean used brass thoroughly because I can and it looks pretty. (LOL). Also, it keeps the dies clean and there's less mess at my reloading bench, which is in the house where my cleanliness-obsessive wife patrols. I'm retired and have way more reloading time available than shooting time. I even swap out media between cycles in the vibratory cleaner. First pass is corncob-walnut shell mix, then brass goes sonic with Simple Green, rinsed, dried, and back to vibratory with corncob only for poliching. I always use dryer sheets - I find thAT the dirty stuff out of the brass sticks to them. Media lasts much longer. Nice to open a box of ammo and see nice shiny stuff. I doubt it shoots any better, but I like it.