What I liked about it, in particular, was that she not only demonstrates the technique, but she describes the essential reasons as to why it works so well. Obviously, if your goal is to have variation in the wash, the technique isn't your go-to, but needless to say, I tried it:
So, to me, it worked like a charm. Simple and accurate, not even a "practice makes perfect" moment here, it just came together immediately. Now, of course, practice does make perfect when it comes to doing the wash in situations where it's not just an easily defined shape, but I think if you pay attention and go with a smooth hand, it will just work.