While this can be done with two people (tie the cord to a ceiling point, pass bobbins across the space to each other), Kolfinna taught me this one-person method. The key phrase is “Under Two, Around the Middle” and the moving bobbin will alternately be the left-most or right-most bobbin. I hope these photos help you learn this method.
[1] When I set this project down mid-braid, I secure the threads in a comb (or a "fake comb" made from paper). This helps me see the next moving bobbin and the three that just finished moving when I stopped.
[2] Setting aside the comb, I hold the threads so that the next moving bobbin is identified. A is off by itself (left-most) and is going to move first.
(The key phrase is "Under Two, Around the Middle" and the moving bobbin will alternately be the left-most or right-most bobbin.)
[3] First, A goes under B and C...
(The key phrase is "Under Two, Around the Middle" and the moving bobbin will alternately be the left-most or right-most bobbin.)
[4] ...then A comes in front of (around) C.
(The key phrase is "Under Two, Around the Middle" and the moving bobbin will alternately be the left-most or right-most bobbin.)
[5] Tighten everything up
[6] D is off by itself (right-most) and is going to move first.
(The key phrase is "Under Two, Around the Middle" and the moving bobbin will alternately be the left-most or right-most bobbin.)
[7] First, D goes under C and A...
(The key phrase is "Under Two, Around the Middle" and the moving bobbin will alternately be the left-most or right-most bobbin.)
[8] ...then D comes in front of (around) A.
(The key phrase is "Under Two, Around the Middle" and the moving bobbin will alternately be the left-most or right-most bobbin.)
[9] Tighten everything up. B is off by itself (left-most) and is going to move first.
(The key phrase is "Under Two, Around the Middle" and the moving bobbin will alternately be the left-most or right-most bobbin.)
[10] First, B goes under A and D...
(The key phrase is "Under Two, Around the Middle" and the moving bobbin will alternately be the left-most or right-most bobbin.)
[11] ...then B comes in front of (around) D. Tighten everything up. C is off by itself (right-most) and is going to move next. Repeat forever.
When it's time to pause, secure the threads in a comb, with the three finished recent working threads together and the one that moves next secured off to the side. Then you'll know if the right-most or left-most moves next.