This guy appears to be dividing on his own. Can I speed up the process? The cap is mostly two distinct forms now, and you can see the trunk is branching... Would it suffer either half much if I divided the trunk with a razor? Sharp scissors?
I know, its a crappy picture I took with a phone. The ufos are reflections from the flash, I think. I took the picture when the lights were out... once they come on, this guy fills out huge, and you can't even see the two distinct parts any more...
I've successfully propagated softies/leathers by slowly "strangling" them where I want them to divide - usually with a cable tie that I adjust a bit tighter on a periodic basis.
I've also successfully propagated softies/leathers by cutting them with a clean sharp knife or fragging scissors (remind me of surgical scissors). In this scenario - any cutting I've done has been outside of my display tank, so that the resulting toxins released by the animal being under stress are on in the main system. And I'll often do a few water changes in the isolated holding container post separation before putting back into the display tank (over an hour or so - being mindful to drops in water temp).
I'm not sure if the rock these are on can be taken out of the tank to cut them apart - but if it's not, you might try using a popsicle stick or something of the like to gently apply constant pressure between the two sections until it starts to further divide on its own.
Just take a razor blade and cut it. If you want to attach it, you can use a technique like I used with my sinularia. I used the notched plug method with my toadstool as well and it was attached in a week. I think you could get by with a tooth pick instead of the gum picks I used. Toadstools aren't as slimly and less apt to slip off the pick.
This is what it looks like today. I've cut off full-sized pieces 3 or 4 times since this first posted. You probably recognize some of its neighbors, Chuck!