Need Help On Sin Green Farming

Sorry if this already been asked...

However I took interest in the look of Darkroot Daggers. However I can never really get the drop from the boss that holds them. He's located just outside of Amatz Basin. Can someone run through this or give some tips?

ty in advance.

Keep killing him until he drops. Took me a while to get them as well, but the green drop weekend helped with that.