If i remember correctly there are 3 forms of haki, being able to predict movements, being able to become shielded (raleigh blocking the elephant and then attacking luffy) and finally king haki. Luffy is in fact using the second form of haki to block (its not a shield raleigh uses but rather reinforce's his palm to block the elephant). So basically its prediction, armament, and intimidation are the 3 forms of Haki with intimidation being the rarest. The prediction also lets those who mastered it know where and who is nearby (as raleigh demonstrated by knowing where all the animals are on the island). So in fact Luffy is using armament haki to its best effect, shield and weapon.
Good chapter, expect Hodi to get downed already and not keep the fight going.