hyougoro only knows the concept behind it
he doesn't know how to teach that ability because he doesn't have the required type of haki, only luffy has it which is CoC
he told luffy to keep doing it while he remembers how he did it the first time, so he can get used to it
luffy used it again to break yamato's cuffs, he needed to concentrate/deep focus
he still doesn't understand how it works so he does it out of memory
the same way zoro was using iai shishi sonson/rashomon, he doesn't understand that what he did was haki but he was capable of doing it from remembering the feeling of being close to death
that's how luffy was able to do it before understanding how it works
he was fighting kaido aside from the red rock attack he was mostly using regular ACoA because he doesn't have time for concentration
until kaido hit him with ragnarock then he figured it out
now he can easily do it without needing to deeply concentrate