Colleagues at the University of Bristol and I are working on understanding how face coverings/masks filter our potentially infectious droplets.

As of mid-August there is a preprint  on arXiv:

Efficacy of face coverings in reducing transmission of COVID-19: calculations based on models of droplet capture

by Joshua F. Robinson, Ioatzin Rios de Anda, Fergus Moore, Jonathan P. Reid, Richard P. Sear, C. Patrick Royall

Code written by Joshua Robinson (University of Bristol) and I, that was used for the calculations in this work is on Github here.

The pdf of the slides of my talk entitled Some simple physics of corona virus transmission at SOFT MATTER: THE UNSEEN SCIENCE ALL AROUND US is here I cover both simple models of person-to-person transmission of SARS-CoV-2, and of masks/face coverings.