Next time I'll have to go with heat... you only heat the area around the bolt as opposed to the bolt itself, right? If you were to heat the bolt, the bolt would expand and make the problem worse. Is my thinking correct?
This is correct. Don't heat the bolt, but the area around it. It smokes like hell, but I have also gone a step further and hit the bolt with WD-40 after heating the area around it. This helps cool the bolt quicker and lubes at the same time. Just don't spray when the flame is on
