I used the "fire" method successfully after soaking an engine for 8 months in various concoctions. First time I tried fire, it did not work. Second time, no worky. Third time was a charm but I did it different. I filled it with leftover coleman fuel, burned it until it was out of fuel waited 5 minutes for safety, and repeated. After the third fire I hammered it like heck and it came free but what still a B until it cleared the cylinder.
I never heard a pop either and it did not move until I knocked the stuffing out of it (and damaged the cylinder). That was ok, I wanted the rest of the parts.
The burn time was about an hour for the three burns. Depending upon how much fuel you can get into the cylinder, you may have to do more or less. Just keep heat on it for an hour.