Access licensed files only after admin changes order status to completed
Sorry I don't have time to watch the screencast.

You could create two rules, the first which trigger when an order is payed in full, this rule could change the order status to pending.

Then you could make another rule which triggers when an order is saved, with the condition that it is in the pending state, it is changed to completed (which allows access to the files).

This could cause complications if you actually use the 'pending' order status for other workflows, in which case you might need to make a custom status you can use as an in between for your review process (using this module https://drupal.org/project/commerce_custom_order_status).