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For the record: I'm not saying masks are completely useless (- again, they will stop droplets -) just that they are a comparatively minor mitigation measure (but they turned into a much bigger and more controversial issue via politicization and the fact that they are an instant visual signal).
No one knows if a person washed their hands or not - but it's easy to see if someone is wearing a mask.
Hand washing is far more important as a behavior prior to and after any type of social interaction. It is probably the single most effective mitigation measure when the most prevalent cause of spread was tactile. Cleaning of surfaces, especially in bathrooms & kitchens is probably the second most effective mitigation measure, followed by avoiding gatherings, close contact (social distancing), practicing overall personal hygiene, and then masks.
As far as the second most prevalent form of spread (aerosols) there is very little to be done to protect from them since coughing & sneezing are often involuntary and since masks don't stop airborne-sized molecules (which could include Covid-19 among other infectious diseases).
The best advice - stay far away from anyone who is coughing or sneezing, avoid gatherings & any close physical contact (especially indoors), practice social distancing.
If you are the cougher or sneezer - head for a door or window if you feel it coming on and try to cough or sneeze outdoors & away from others. Carry something to cover your mouth (again, as with masks, this will do little to confine or contain aerosols, but may help limit the distance you project them). Use your hands to cover your mouth or sneeze into your elbow (then wash afterward). Wash your clothes regularly if you've been around others, if you're coughing or sneezing or around anyone else doing so. If you have a chronic cough or sneeze, stay away from others & public places. Keep your orifices clean - brush teeth regularly & increase the use of alcohol-based mouthwash. Use a nasal cleanse & clean the ears with hydrogen peroxide on a Q-tip. Focus on a diet & supplements that boost the immune system.
And now, of course, get vaccinated.
None of these are cures, treatments or 100% sure-fire preventative measures - but they are things that may help mitigate spread depending on the circumstances, and slightly lower the odds of spreading or contracting the virus.