i grew up in the rust counrty.... when heating up nut and stud you focus the head on the nut it will expand biggity bam it comes loose, when heating a bolt focus the heat on what ver the bolt is in.

also if it's a nut, take a chizel and hammer smack it in to one of the flat surface's a wrench would hold. this sounds weird but it works!! really well,this is how i get off old nuts on aircooled vw exhaust.