Use Poison Mist to shroud the battlefield, then attack with one of your several ranged attacks.
Great Heavy Soul Arrow is used here to throw off the timing your opponent might have. Nobody expects you to use it, but it still deals quite some damage and homes a bit.
For even more damage use Crown of Dusk/Tin Crystalization Catalyst or both.
Be wary of people who will use your mist to their advantage as well and always be prepared to fight with your Moonlight-greatsword alone.
