The following method works great for me:
Get a bowl of tank water ready, get a breeder basket net that hangs or clips on side of tank (buy a plastic hang on container that the fish store uses to hold bags while getting your fish & drill a bunch of hole in it), just any container water will pass through, cover bottom of container with calcium carbonate gravel, now with a scalpal or new razor knife cut/scrape off mushroom from substrate, place in bowl of tank water, harvest all the mushrooms you care to this way, then place/pour bowl of tank water & cut mushrooms into container hang on side of tank with gravel in it, slowly flip them all right side up, now forget about them for two weeks, after that time they will all have attached to gravel pieces that are easily super glued to larger rocks for sale or trade. Hope that helps. Getting the right container is the hardest part of project. Also if you place the container on the side of the tank with the return nozzle; you can rubberband a piece of airline tubing sticking well into return and place the other end into your mushroom container for a little flow over them!