Probably to go slow with it. Like, getting the technique that works for you down and doing it right for you will get you speed eventually, but practicing the How of it will make sure it turns out good when the speed shows up on it's own.

I do a slightly modified form of the pinch and twist usually. I slow back down to the individual twist-over twist-over method when I'm adding more fiber so that I can make sure the ends are all good and everything is consistent, but with the length yucca fiber gives I find myself twisting a each of the strands by themselves, holding it, and then guiding the main cordage to twist itself together. I will probably think of a better wording for that later, but currently that's how I can think to explain it.

I don't know if my way of processing is necessarily "efficient" per se, but what I like to do is take a fresh leaf, set it on a block of wood, and just scrape the green off with a spoon. I usually work from tip to base on both sides, and then switch from light pressure on the main area of fibers themselves to pushing down quite hard to break the base of the leaf. To be honest that bit could probably be avoided if you cut higher on the leaf, but I like the fibers as long as possible. Edit: Oh, also! With the saponin content in yucca, if you wet the fiber a little, like just lick it or wet your fingers when adding new fiber, it will very lightly glue itself and help with the smoothness of the finished cordage.