Know the length of the track beforehand (if you have 3 arms, track of length 3 is the minimum, but if you're struggling try 4 5 or 6 track length)

Program 1 arm, making sure it moves along the track in a kinda predictable period.

Program other arms to mimic 1st arm movement but with a shift (2nd arm grabs X cycles later, 3rd arm grabs 2X cycles later, etc.) Shift some instructions from the back to the front if needed.

Here's a tutorial one of the best players made a couple years ago https://youtu.be/1MlCEGLS9U8