Trying to Build up posture when he is full health is useless. Just bait out the moves that lea e him open for attacks (Big thrust attck/Shadowfall and his vertical chatging strike). Using firecrackers will make this easier. When he has half health left start deflecting and fighting as usual. Beware his firecrackers, these are best countered by dodging to his right, which allows for a hit or two. Second phase is easier than the first one in my opinion as his owl attack is almost always followed by the big thrust and when he disappears, after jumping to the ground from the owl he is exposed for a couple of hits. It's a matter of perseverance and patience, but won't take you too long if you do it correctly. In fact, I think this is one of the most enjoyable fights in the game. Hope this helped you in some way, even if I am a bit late.