If you've got acetyline available, skip all the hassle of trying to spot anything onto the seized bolt. Just get out the Victor hot wrench and get 'em warm! A small heating tip like a #0 or a #1 and a needle-point flame can be controlled very nicely to just heat the bolt without doing much damage to the surrounding area.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!