Good green screen workflow

I have a 30 min interview of a subject against a green screen. I'm cutting a piece in FCP where I will be coming back to this interview several times. I'd prefer not to "send to motion" to key out the background each time we cut to him after the piece is completed. I tried sending the whole 30min clip to motion and bringing it back to FCP before editing the sequence, but you can't bring the audio back via importing the motion project file. Another option is keying out the green and exporting to animation + alpha with audio, but the file size ends up being huge.

Is there a better what that I am overlooking to use motion to key out the green on the raw footage so that I can then cut with the keyed footage and audio? I really don't want to have to do multiple "send to motion" tasks after editing the piece.

Thanks!