The first embedded video (36 seconds) shows how to blur all faces in a video.
The second embedded video (1 minute 33 seconds) shows how to customize the blurring effect.
The 3rd embedded video (37 seconds) simply shows what a customized blur looks like when completed (it is the result of the 2nd video you see above).
Here are the steps to follow.
1. Select enhancements (looks like a magic wand) - the second option next to the pencil.
2. On the right-hand side select blurring effects.
3. You then have the option to blur all faces or the option to customize the blurring effect.
As always, let me know if you need anything!