Post processing: Sand around internal edge, especially around nose. Spray down with sealant (silicone spray, clear laquer, flexseal, or paint for micropore blockage and easy wipability). Attache either (2) tourniquets cut into 1/3 to the hooks, or elastic bands. many sizes can be found online. Approximately 8 mm is a good width, but anything can be made to work.

Follow youtube instructions for installation of suggested filters: https://youtu.be/ySOCNycv-aA

Estimated to be n85-n95, testing in progress. Wear over face mask for additional protection and comfort, boosting to (unverified yet) n95 or above. The most important thing is the seal. you can experiment with rubber door seal material around the edge, but sanding and then putting in hot water and molding to your face like you would a moutguard, works best. This is a last resort attempt at "better than a bandana", with no guarantees but my best attempt at an n95.