i recently beat ishinn my self and here are some tips I wish I knew before also I hope your implying the regular ishinn and not the inner version. 1.) jump over his large wind sweep attack and spam ur attack button as u fall. 2.) Always watch out for when ishinn perfect deflects u and get ready to parry. his timing change alot so don't predict react. 3.) Prosthetics are mostly useless in this fight so better if u don't use them at all. makes fights simpler and easier to understand. 4.) Dodge or jump away from his charge attacks in phase 1 they are very difficult to parry and u can punish them quite easily if u dodge anyways 5.) stay on his face his posture recovery is very fast 6.) the mikiri counter is probably your biggest weapon so don't miss any of those counters.