The “Quick Cut T-shirt Face Covering (no sew method)” is the simplest of all the methods I’ve seen. All you need is an old T-shirt, a sharp pair of scissors, and a measuring tape.
I wasn’t going to reply to this because I love that you’re wearing your wife’s pink bandana, and I don’t want to be that poster, but this has been concerning me since yesterday. Wearing a bandana Old West outlaw style gives you almost no protection.To provide any significant level of effectiveness, masks need to be closely fitted to the face. Homemade ones should have bendable wire to provide a tight fit over and around the bridge of the nose. Your goal is to stop air from getting in anywhere other than through the multiple layers of fabric.
Best wishes for good health!
Thank you, and I did wonder just how effective it would be. My sister sewed a bunch of masks, and is sending us a few to use, so we should be in better shape for that shortly.
(I also see that the CDC’s homemade mask guide includes a way to use a bandana. 
)