Spiralling is the time to catch it, so it is good you're recognizing that, sliders. (ElsaMars' post reminded me.)

My main coping technique is distraction, usually taking the form of dvd watching (not enough concentration to read, but if you can, go for it.)

Getting into motion is good. Outdoors is good (if it's not too overwhelming). Walk. Run or ride a bike. Maybe put on some music and bop around a bit to it.

Take a shower with a washcloth or loofah or something and do a good scrubbing. Get the circulation going. Maybe finish the shower with an icy blast.

Do you do art? Sometimes people like the brain space doing puzzles brings. Have you tried coloring? It's very "in" in the world of distraction/re-focus these days.

I know. It is not easy, even at the "lesser" levels of depression. But so worth trying. Might not pull you out, but they can fill some gaps of time at least in the meanwhile.