It will smooth itself, it is just a zinc coating super soft. Just slice a circular object and let it run circles for 20 minutes it should be perfectly smooth after that. The bearings squeeze the zinc right off.
Do something like a large tube spiral vase with no top or bottom layers and just let it run in the air. You can even tighten up all the bearings a bit to really get them to bite then back them off a touch when its done.
You’ll see the metal dust start to appear and it will even squeak a bit, kinda funny.