I take a pair of coral pliers to the surrounding rock and try to break off the rock or at the very least some of the material the foot is attached to. You can scalpel them off, I do it all the time, but it takes a while before they can re-attach. If I were you, I'd pull the rock and see if they can be easily broken off. If not, use a razor blade and try to get some material off along with the foot. If you can't, don't worry, but you'll need a place where they can re-attach to a piece of sand or substrate.
Have you ever heard of Talenti Gelato? You can get the stuff at Kroger and it's very good. For our purposes, the clear plastic containers make great mushroom nurseries. I put a handful of gravel or busted pieces of coral in the bottom and let the mushrooms sink to the bottom and leave them in the tank for a week or so. Pay attention that they are on substrate and not the plastic side of the tray. Given the option, they always seem to attach to the smoother plastic.
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