An Easier and Safer way of killing Greenbrier vine is this. Purchase 3" X 5" 3 mil Poly Zipper bags, available on the Internet. Cut large 100% Cotton Balls in Half. Put one Cotton Ball half in each bag. Add a couple drops of 100% Brush Killer to each cotton ball. Cut the Greenbrier vine and place the Zipper bag over the cut, sealing it around the vine end.
I don't see a question there, but thank you for sharing your technique.