Soaking methods for insteads

I've been using insteads a lot lately, and I was wondering how I should clean a cup for reuse after a cycle. I feel bad throwing them away... I tried my usual method for my other cups -- swabbing it with alcohol, and it still felt slimy and I couldn't get gunk out of the crevasses. So I think I'll probably have to soak it to get it clean. What are all the soaking solutions you can use for cups? Or does anyone else have a different method they use?

EDIT: I guess I'll just stick to one cup per cycle. And I'll look into getting a diaphragm to use instead. No pun intended!! :)