USB music manager

I'm on a mac and trying to find a application that can manage my music on USB drives. I use CDJ 400s and love using my thumb drives but I hate having to reload all my tracks since I put it into itunes. I would love to have it sync like itunes but there is no app I can find that does it other then Double twist and it is super slow. Anyone have a basic manager for thumb drives?

Edit: just tried double twist and that doesn't work well either. It doesn't create folders for the usb drives with its playlist.