My engine builder who has rebuilt a hundred 2Fs (used to be Man-a-Fre's builder and K&H LC) used Never-seize regular. I watched him do it. He coated the entire bolt, with a dollop under the bolt head. He wiped excess off the bottom flat of the bolt, leaving a thin smear. Head was cut so he used washers under the Head Bolts and coated the washer with anti-sieze. After torqueing sequence, he wiped away excess.
As stated above, important to clean out the block holes with a flat-bottom tap. They're a little hard to find. If you have new head bolts you can cut a couple grooves into an old bolt and use that.
Just my preference, but I wouldn't use an impact. I gradually loosen in reverse order of tightening. Probably just me being anal, though.