I printed this mask in PLA (it uses standard N95 filters) using 0.1mm layer height on my Prusa I3Mk3. Post printing I smoothed with a little fine-grit sandpaper, primed with automotive sandable primer, and painted with cheap craft acrylics (Apple Barrel and similar). I later added some fine details with a black technical pen (see 2nd photo).
I also used closed-cell door weatherstripping to seal the edges. Did an adequate, but not perfect, job.
If you print with ABS, a cold acetone vapor bath and/or buffing with acetone and Q-tips can smooth the print lines. Note that this can discolor the filament finish, so plan to paint afterwards.
Note that the model required modification of the interior to improve air flow from the filter holes to the mouth/nose. The original design was too snug for my face.
Near-final paint job
Final paint details: