Worked out well. Ran the box fan at both medium and high speeds with
the filter across the front. I'm a little hesitant running the fan at
max for extended periods because it seems like the filter constricts the
input air flow. In any case, I did soldering, heat shrinking with
matches since my lighter ran out of fuel, and even marked some wires
with nail polish. No trouble at all. I expected the most lingering
smell would be the nail polish, but even that I could barely detect.
For $13 and the cheap box fan I already had, job well done!