Rookie mistake

[Oxymoron]

I placed GSP in my display tank on a piece of live rock. It has since spread from the frag plug and began to cover my live rock.
I have since removed the frag plug and placed it in the sand bed but now I need to know how to take out the GSP from the main rock.
After researching a bit more it seems that GSP can slowly take over a tank if not dealt with and should probably be kept in the sand bed away from the main display rock.
Does anyone have any tips or tricks to kill off GSP. Im thinking of pulling the affected piece and using a propane torch to burn it off. Any input would be helpful.
Thanks