I inherited a nice little upholstering needle after my great grand-mother, who was a dressmaker.
When I was stitching the cord I made the sharp ends first with my fingers.
The uphostery needle seemed to me as the only way to make the cord go through the fabric. Certainly I couldn't have done a knit at the end of the string, I use a thread.
This is how I stitch it - simple, easy, it's the nicest thing to do about these lillies for me :-) Just stitch through the string in the middle (between the two cords) and then to the same place.
The finishing was cruel. I'm not very handy and I wanted the end not to be visible. I've untwisted the cord and worked with each of the pieces separately.
So - this is it.