How does two layers of a cotton bandana work compared to an actual N-95 mask?  I imagine they aren’t comparable, the bandana certainly doesn’t seal, but may give a false sense of security.    
It helps you not share the virus - and perhaps a little from not getting it.  
I second that.  We have probably all seen pictures of people going to extremes for costume protection (even full SCBA gear!) A cotton mask probably controls the cough/sneeze trajectory from a sick person better than filtering out particulate from others.  For a person who 
isn't sick, the barrier is likely more psychological than physically effective leading to a a false sense of security.  I personally will stick with frequent hand washing and physical distancing more than wearing a "home made mask".  

I've been working from home for the last 5 weeks now and have only been out in public a few times (for grocery shopping/car repair and 1 meeting).  My province also has almost nil infections compared to other jurisdictions.  My concerns are more economic based than with getting sick.