Let me tell you a stupid story of desperation.

I have several Christmas cactus (Zygo sp.) plants that I LOVE and have been hauling around with me for several changes of addy so far. One of them started showing the dreaded signs of root rot- wilt, refusal to perk up with watering, funny smell. I FREAKED and gave it the backwards treatment, just on a hunch... I've never seen this described elsewhere but this is what I did:
I sprayed the leaves with wilt-pruf.
I took the plant entirely out of its pot and put it in a big somewhat squat for its volume terra cotta one, but did not backfill any new soil.
I put a plastic shopping bag over the foliage and placed it in flourescent light (=on my desk at work, lol). I blew into the bag whenever I rememberd too, just to change out the stale air under there and give it some CO2 and moisture.
The soil started to dry out rapidly, but under the bag, the plant was not losing water through transpiration. When the dirt felt like it was to the point where it would normally NEED to be watered, I backfilled the pot with fresh soil and gave it just a LITTLE drink.
When it looked like it was perking up, I took the bag off.

It worked, and if I ever get to the point of desperation with a pot plant, I might try that method.