This ^^ works well.A quality penetrating fluid is a must have for those stubborn bolts. Ive tried it all, WD-40, Liquid Wrench, PB blaster, ReleaseAll to name a few. Release All is pretty good, but rather expensive.
My home [garage] made stuff works better than anything else I've tried off the shelf. 1 part atf [cheap no name +3] : 1 part acetone in a dollar store spray bottle. I only mix what I need for the job as the acetone evaporates quickly, however that is what makes it so effective. It pulls the atf into the threads.