FWIW, the few times I had an outbreak, my dwarf angels usually took care of it. (potters angel or flame angels).
You can also try smothering them with epoxy and then removing the epoxy later.
Blowtorch worked pretty good for me on a couple rocks. Be careful if you try it, I read somewhere you can explode the rock if you heat it unevenly. Didn't happen to me but prudence dictates that I repeat the warning that was given to me
