Yes, you can apply your auto-refund policy when cancelling a session yourself. When you go to cancel an individual session or series, where auto-refund is in place you will see a check box on the cancellation confirm pop-up that gives you the option to apply your policy to the booked places. The policy is applied as if the customer cancelled the session at the time of your cancelling. You cannot apply the policy to sessions that have finished.
Please note that in order for your auto-refund policy to work when cancelling a session as an admin, you would still need to cancel in line your cancellation period. For example, if you have a 24 hour cancellation period on your auto-reruns policy, then you as the admin will need to ensure that cancellation is actioned in line with this period.
If you wish to cancel a session as an admin that is outside of your cancellation period and you'd still like to issue an auto-refund to all attendees, then you would go to Schedule > click Details on the relevant session > Edit this session > within Step 2: select your cancellation period of the auto-refund set up wizard select Anytime > complete & save new auto-refund cancelation period > Update this session > Edit this session > Cancel this session > tick the checkbox next to Apply any auto-refunds that may be due in line with session's cancellation policies on the pop-up > Cancel.