I'm going to tell you a little secret. I never actually "trained" this skill. I just tried it one day and didn't have it. And then I tried it a year later and did.
You might be thinking, "Well, that's not very helpful, Jessica."
Well, the thing is, I was training the strength I needed for a single toe hang, I just didn't have that in mind. After I quit my day job, I had a lot of time on my hands and began a yearlong process to become a Gyrotonic trainer. I suddenly became very aware of my feet. Mostly, that I couldn't seem to control them. But I kept working on it and slowly gained balance and articulation, and I started to understand why our feet are so important.