While Luffy initially learned the basics of Haki during the two-year timeskip between Episodes 516 and 517, he did not master its advanced forms until much later.
In a desperate moment to save himself and Hyogoro from explosive collars, Luffy subconsciously uses a level of Advanced Armament even higher than what Hyogoro was teaching— Internal Destruction .
Luffy begins learning Advanced Armament Haki around Episode 929 in the Wano arc’s Udon Prison, achieves emission around Episode 939 , masters internal destruction by Episode 950 , and successfully uses it against Kaido in Episode 1015 .