Phasing Noise

After 15 months and numerous casts, I'm scraping my latest micro-budget project. But, I do want to make a demo movie for some of the cast members. But, I don't plan on spending anymore money on this wasted project.

Since I'm not going to do ADR, I'd like to try and clean up the existing audio as best I can. Most of it is crystal clear. But, some has underlying room tone noise (radiator, refridgerator, water bowl etc) I've used the dehummer/Noise reducer and it helps.But, I'm told by a music engineer there's an old audio trick where you take a piece of the room noise and play it at 180 degree out of phase and in perfect time with the existing track and the two will cancel each other out. Supposedly it works better in theory than it does in practical use. But, sometimes it works like a charm.

Does anyone know how to play a track 180 degrees out of phase of the original? Supposedly 180 degrees is not running it in reverse. I've done that it does nothing.

THANKS!