I use a pair of surgical sissors to cut the top of the mushrooms off (leave the base on the rock) and then either cut that in half or leave it whole and place it in a plastic container with cc in it and leave it so the corals can heal up and not be blown around. You can also use a razor.
If you cut the top off and set the top on some rock in low flow (or plastic container like I said) you will end up having two mushrooms where you had one.
If you cut the top into two, then you will have three mushrooms.
If you cut it into quarters, you will have five.
Etc.
The more you cut it the longer it takes for them to heal and the more likely they won't make it. It also depends on the species to how well they heal and can handle the cutting.
Cutting them in halves gets the most success imo and usually you don't lose either half.
When you cut make sure to swirl the piece around a little in some tank water to get the brown ooze off the mushroom. If you don't get it off it could lead to a infection and death.
