Canon 500mm mkii Playback ring

[hobsey]

I fancy having ago at videography with my 500mm mkii lens and seen the playback ring is designed for such uses.

Problem is, the user manual isn't particularly clear and was wondering if there is an online guide on how to use it along with the present buttons.

I've tried googling and YouTube searches but there seems to be a lack of information and I can't be the only one that has wanted information on these.

Thanks in advance