AJ, thanks, great educational video for many, and I'll take the opportunity to add an extra trick for people, like me, with glasses, using a 10-12cm 3M micropore stretch. This makes the nose bridge fit airtight without your glasses getting fogged up. 😷
Note: I've a difficult nose😇
I’ve made a video on how to put on an effective mask to better prevent Covid infections after hearing about David Lynch
This does not constitute medical advice, and look into fit testing with your assistants if you want extra security
However this has worked for me