As long as little pieces of rubble any gel super glue or reef glue will work on the rubble. If you’re going to wedge it inside you may as well glue it. Preventing from getting dislodged and blown somewhere. Also, correct gluing the body of a mushroom is difficult. It will come off later. But if it’s attached to rubble easy. Also, another trick if you want them to spread faster. Take a razor and slice them in half. Sometimes they’ll grow back together, but doing a few times and you’ll have lots of them. Faster than natural splitting. Assuming ideal conditions, they should be able to take the beating.