Yep I agree about compression. Don’t see that helping unless he was suggesting using a side chain to trigger a dip on the off mic? Good lck with that!
I think it’s a mistake to edit out the off track. That’s too severe. You need to be mixing down the off mic so the on mic I’s definitely featured, but a little of the room tone will remain in the mix . It’s called bulldozing, as the faders work like a bulldozer diggers controls. It’s just mixing. Everything needs mixing before it goes anywhere, even just a single mic needs eq,ing and level adjusting.
Why it it a problem to invest time and effort making the audio track correct. Audio is just as demanding as pictures to get the right results and arguably bad audio is more noticed than bad pictures!
It may be that your problem is made worse by poor mic selection at the recording. My preference is the cos11.. Poor mics may have a wider pick up than you want, and of course the levels need to be correct.
Peter
Post Production Dubbing Mixer