There is nothing that will be 100% with a lay person.
Even if the lay person wore a biohazard suit designed for the worst of the worst...they would screw something up and cross contaminate.
You do the best you can do to reduce the viral load. I do a number of things. So far they have worked. I expect Covid has gotten through my barriers. I then kill them off in my nose and mouth.
Yup...I’m sure those in Wuhan that created this virus had the best of the best protection. Oh...and with OUR tax money!
And I have done nothing. I don’t wear masks, when forced mine is made of mesh. I travel, meet in large groups and shake hands. So far nothing.