Home made cloth mask

If you can think of it, somebody at NIH has used tax dollars to test it.

A mask doesn't have to filter individual viruses, it has to filter aerosol droplets. Transmission of disease requires a transmission of a viral load that is capable of overcoming my immune response, which is pretty robust for oral ingestion, less so for nasal, and quite limited for eye entrance. The t shirt mask was less effective than the N95, but still achieved N60 or so, a significant reduction in exposure.
Too, using the mask successfully requires discipline and training, proper fit, and that sort of thing. Put a mask on an untrained user and it is a talisman, not ppe.
The masks are designed as disposable items because, if used where they are needed, they collect a LOT of virus load on the outside of the mask. Washing the mask, whether synthetic or cotton, will remove the viral load, but have an undetermined effect on the filter mesh size. And the disposable N95 masks are rated for single patient encounter use: no one is quite sure what will happen if you wear the same N95 for 12 hours-virus may well migrate over time from the outer surface to the inner surface.

And then there is the possibility that masks don't work anyaway.