The key-word of the split focus technique is: focus. The manipulator directs the attention of the audience: to the puppet, to the puppeteer or both. Shifting the focus from one to the other. Split focus is the experience that the puppeteer completely disappears in favor of the puppet.
What makes a puppet alive? The connection between the puppeteer, the puppet and the audience. All depends on focus; in what way do you transfer focus to the puppet. When the puppeteer is not part of the composition, the focus shifts to the puppet. When you are visible, you are competing with the puppet for attention. Use this wisely. If the focus should be on the puppet, make it so; when you are interacting with the puppet the attention can shift between the two of you.
The first step to bring the puppet to life is to transpose both breath and bodyweight (countermovement) to the puppet. Once the performer controls this part of the technique, he can go on to the next level: convincing the audience that the puppet breaths and moves undependably.