1. Back up before conversion
Before changing formats, make a local CUE backup of the USB or library you are working from. Conversion creates new files and may change how the Device Library points to tracks, so start from a state you can inspect and return to.
2. Identify the FLAC/WAV files that need MP3 copies
Do not convert the whole library just because a few files may be risky. Focus on FLAC or WAV tracks that need better CDJ compatibility, especially for older players, rented booths, festival changeovers, or USBs used on unknown hardware.
3. Create CDJ-friendly MP3 copies
Use a conservative MP3 target that your expected players can read reliably, and keep the original FLAC/WAV files untouched. Clear naming helps you tell source files from converted files when reviewing the USB later.
4. Keep playlist and cue context visible
The hard part is not only making an MP3. It is keeping the library understandable: which playlist used the track, where the converted file should appear, and which cue or analysis context can safely follow the conversion workflow.
5. Verify on test media before a real set
Treat FLAC/WAV conversion as a compatibility workflow. Generate or preview separately, then test the MP3-ready result on a separate USB and, when possible, on the kind of CDJ setup you expect to use.