Yes and no! You can’t use it straight away, then nothing will show up on the 2000’s and vice versa. You will have to put USB back in to the computer. Fire up Rekordbox and choose the CDJ’s in the settings. Then you just ”eject” again. It’s during the eject that the library writes to the USB and then you can use it on the 2000’s.
I’d recommend that you keep 2 sets of 2 USB’s if you want to avoid ”messy”. Update them 2 at a time, not all at the same time. If anything goes wrong, believe me when I say it will happen sooner or later, you’ll be very happy to have 2 USB’s you know works, even if you won’t get to play the last tracks you put into Rekordbox.
And yes, 2 of them. If you enter the club, load your 1 USB and discover that someone ”borrowed” the lan cable or if it’s gotten broken, you’r f****d. Even if it’s not your fault, in most cases you’re expected to have the gig under control as long as you have 2 working players. Any excuses why you don’t, won’t do you any good.
Use only good quality high speed USB’s and updating them will only be a few minutes every time. If you’re on your way in to the clubs, this is how you need to prepare, at least. If you have descent laptop with Rekordbox, you can always bring that for either running Rekordbox just to deliver the tracks or in performance mode to control a CDJ-2000/DJM-900Nxs or NXS2 setup.