There are one or two U tube postings on that theme - each guy has a slightly different take on it - but same principle. It really is the heat that does the job - gets the heat down the block on to the threads - which is hard to do otherwise.
Mig is probably the smarter course for small stuff like that - harder to control the heat on arc. But not impossible if that is all you have.
I had one job I was afraid to tackle - on an expensive Al head. Gave it to a local specialised auto machine shop and they did a good job using spark erosion.
U tube has lots of handy w/shop tips - which like Steps said - are probably never new - just forgotten or not discovered (by you). Some rainy day it is worth poking around on them. The trick is to remember them when you need them - getting harder every day.
Alan