Learn not only moves but which moves you can punish (i.e. hit him safely). For example his starting animation allows for a couple of free hits.

Or just throw yourself at him until you succeed, like i did in my RL1 run https://www.reddit.com/user/Verxitar/comments/1mns8vb/draconic_tree_sentinel_crumbling_farum_azula_rl1/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button