I've had good luck taking small slices out with automation, never tried ducking. Is it fast enough? I don't know. I do know doing a bunch of them with envelopes isn't.
..fast enough.
Dig in and fix the problem like a man and don't heed the nonsense of those who dare not face a trying task of their own design. This is easy to fix and you won't mess up your soundstage by using the left only overhead.