You could also say "don't wash hands" because it's not effective unless you combine them with social distancing and other quarantine measures.
A preventive measure does not need 100% effectiveness to be recommended. For example, washing your hands.
The problem with masks is not that they aren't 100% effective, it's that they are worse than no mask. They increase risk.
The only people who should be wearing masks are healthcare professionals are people with the illness who are self-isolating in a family home.
Here's an effective mask: https://twitter.com/missemjo/status/1239520762815488000/phot...
https://twitter.com/kimbo2205/status/1238089278565031936/pho...
Why are you pushing masks to cover the nose and mouth, and not goggles to cover the eyes? Or gloves for the hands?
If the argument is that training is needed to use mask effectively, then simply put out a video on how to properly wear mask. This is how they push out hand washing. They have posters and videos to show how to do it properly.
Goggles to cover eyes can decrease risk, just like mask. Gloves for the hands will prevent your bare hands getting dirty but won't help the spread of of the virus onto other surfaces as you touch things throughout the day.