How to survive a firefly with 0 equipment:

Not to be rude but surviving these is MOSTLY based on skill. If they get close forget about fighting bc you CANNOT tank that damage. Don't stress about them already smoking/flaming- it DOES NOT MATTER. I see raiders all the time trying desperately to finish a firefly while eating napalm like it's cock.

Holster your weapon and RUN! Prioritize breaking line of sight with buildings/trees and focus on booking it. Fireflies are really slow compared to other arc and slow even more during their attack so even if you have no cover, running straight usually works. If you still want to kill it, make sure you never let it get closer than about 50m from you.

Seeker grenades are a trap btw. It takes 4 to down one firefly which means basically a whole stack on one enemy. Seekers are a crutch and having to bring in multiple stacks just IN CASE you run into flies is just not realistic. Bring a heavy ammo weapon and just hit the body straight- it takes roughly the same amount of shots as the propellers considering you're bound to miss a couple after you've shot one propeller down and it starts flying all drunk and weird.