Apply audio effect to audio master buss FCP X v10.2.3 / How to ccess FCP audio mixer

I'd like to apply an audio effect to the master buss of my FCP X v10.2.3 project. For example, I would like my master audio channel to pass through a loudness monitoring plugin such as TC Electronics LM2n or Nugen Vislm - both of which are available in AU or VST plugins. Is it possible to do this?

I'm trying to avoid exporting the project as an AAF and doing this in Pro Tools, and I'd like to refrain from making compound clips etc. Is there a simple audio mixer option I can use?

Any help would be greatly appreciated!
Dan