I have a rather dumb sounding question: Would spraying the front of my mask with Purell

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11. I see some people that wear a face mask and a face shield.

That is likely the safest choice. Virus particles can enter through the eyes, so in theory, if you walk through a viral cloud and some got to your eyes, you could get infected. One technique that I use when coming up on a person who is not wearing a mask is to create as much distance between them and me as possible, then turn my face completely away from them and stay that way for several feet more.

On edit. I honestly believe that the people that get infected, who say that they did everything right, made critical mistakes. Some people consider wearing a face mask to be a situation where they only have the very tip of their noses covered along with their mouth - that is useless, they are sucking in a lot of unfiltered air - the mask should cover their nose at least up to the nostril nose bones, and then a nose wire should be compressed to form-fit around the nose and adjoining face.