when i got my first home, i had to put in about 12 fence post.
i did it with a post-hole digger and the blessed hardware store guy introduced me to the DIGGING BAR!. i think the first 8 inches over every hole was a "WTF am i doing?" type thing, but under that, it dug tough but consistent. i had it down like a ballet. the bright side of clay soil is that the hole is super stable and neat.
it was very satisfying.
my neighbor asked me to help with his perimeter fence..about 40 holes. he showed up with a tiny bobcat with auger..that was super fantastic.
but i dont mind the digging bar. "post hole digger" is misnamed. "post hole soil remover that the digging bar dug" is a better name