Generally we use an underhand grip to rotate the vertical circle. Half a circle and one after another. Note that after you become proficient, you can find that the rotation force is generated by the inside of the thumb. You can also change sticks every 2 turns. But there is a circle around the wrist or palm. I am only familiar with the wrist. The principles of flat circles and cubic circles are the same, but the focus is a little different.
If you still don’t understand anything, you can add me on QQ. I have a better video teaching infinite stick spinning