He said already that the rock can't be removed...
So...
I would just forget the putty (or underwater epoxy). It's a mess and you'll waste your money with it.
Palythoa could release lots of mucus too, making it even harder to do that.
It doesn't work 100% anyway.
Simply use a sharp fine knife and syphon the water close to the polyps while cutting them off the rock.
You can do that while doing your partial water changes and make it part of the maintenance until you take them all out.
If you're careful you'll be able to save most of them and put them on plugs, to be exchanged on your LFS.
Any pictures?
…and be happy.
Don't forget to se gloves and be very careful, so you don't cut yourself.
Make sure the skimmer is good!!
Not a big deal.
Grandis.