Actually, N95 masks are not 100% effective. Additionally, their effectiveness declines over time. Use that as a point of comparison to surgical/cloth masks.
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.