Hot Kalkwasser paste is partially effective. Concentrated NaOH (sodium hydroxide, often sold as chemical lye) will do the trick as well and is reef safe when used in moderation (it is, after all, just sodium and hydroxide ions).
Injections will only work if you have a few colonies to zap. It won't rid a tank of mushroom "infestation." You'd probably be better served with biological control like butterfly fish in that case (Chaetodon lunula, for example).
