Here's a paper that shows that "homemade masks" made from tea cloths were reasonably effective

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2440799/

I'm using a homemade mask made from hepa filter material between two layers of dish towel material when I go out. I tie it around so it completely covers my nose and mouth and extents It will probably help if a person a few feet away coughs at me, as happened in the store today. And if I should cough, I may not infect someone else, if I am carrying.

And it may keep me from accidentally touching my face