vtraudt

Soaking: absolutely
Next: good 6 point closed wrench or socked, try to move nut first
If nut moves, try bolt head.
If bolt head moves: rotate and more soaking.

I then move the nut out a few mm until the bolt is flush with nut, and give it some good smacks.

Pull nut back a bit more (until about half the threads are still engaged) and hammer back.

At that point, bolt is normally loose enough to drive out; trying to avoid mangling the last bolt threads too much.

When putting together again, I clean the bolt and the bolt holes, and apply antizeize.