lay it in there, do it in a well ventilated spot. leave it for about 10 mins, you'll hear it start cracking the deadening. should be as easy as going thru afta with a hammer and chisel and breaking it off
oh, and due to the fact it freezes thru the metal, dont start / drive the car for at least 24hrs........may have snap frozen fuel lines and the like. its fine after that time