[Andrew Maslen]

Quite a few different ways I’ve seen on here to achieve this, but here’s my workflow.

I still use Pluraleyes, as it seems to do a better job than FCPX’s built in Sync.
Once Pluraleyes as done its stuff, it imports all assets into fcpx into a project giving me the ability to assign separate roles to the audio tracks I want to use. Then export separate roles for each audio track (just one step required). Re-import these tracks back into fcpx. Drag the multi-clip that pluraleyes created into a new project, drag the separate audio roles beneath. Multiclip with separate editable audio. I also set the multiclip audio to camera scratch to compare before dropping audio level before exporting.

Andrew