In general, busting has meant using illegal substances to treat CH. People have used them because they very often work better, with less serious side effects, than prescription medications. You can read all about busting in the "ClusterBuster Files" section of this board. Right now, a lot of people are using a substance that is like some of the illegal busting agents -- it's a tryptamine, like them -- but is currently legal in many -- but not all -- places. It's called 5-meo-dalt. It might or might not be as effective as the illegal substances, but it is legal (in many, but not all places).
Since you commented on the other thread here, I'm going to assume you read the posts in that thread, so I'm not going to repeat all that information, except to say that if your husband doesn't have oxygen, that should be your/his first priority. You mention "triptans" there, but you don't say whether it's in an injectable form or some other. Injectable works a lot faster.