****** UPDATE *****
This is the proper format and I have tested with PC on this without Rekordbox.
Use a free PC formatting program called Rufus. Use the settings in the link above.
Than copy your WAV or MP3 files to the USB stick after formatting.
Your XDJ-1000mk2 will recognize the tracks.
Since these just raw music files without Rekordbox "indexes", your XDJ-1000mk2 will automatically render the track on the player, it will not display the rendered waveforms in full. Only half size. If you have a network cable connected (RJ-45) you can use the link feature which works 100%. However, you cannot use the "Master/Sync" feature to auto sync tracks.
If you use Rekordbox to import your playlist (which will auto import your music files), then you will get the full waveform with the beat grid and quantizing feature, as well as the Master/Sync functions. Pretty much like the XDJ-RR display and functions but on a single player which can be linked.
Also tested format using a Mac format "Mac OS Extended" (Journaled) and scheme - MBR (Master Boot Record).
Hope this helps others on this.