How to work on a screw with somewhat less cursing.
A: You may well have noticed that small parts like some screws have an ability to fall and vanish into the aether; this starts the process.
B: A screw with a small, fine-thread shank with a wide head that needs a bit of reshaping is a problem*: how to hold the shank without damaging the threads. You can wrap a couple of turns of tape around it, but if you use a drill or something to spin it you can still wind up with enough pressure to ding the threads.
C: The Idea: get out the dremel**. It uses collets to hold the different bits, and the collets are made of aluminum. Use a collet the shank will just fit into and snug it down; it'll hold tight and keep things centered without danger to the threads, and using low speed and a fine file and suitable grit wet/dry paper you can either shine up or profile the head and then polish it very nicely.
Yes, I did manage to drop the screw once taking it out of the collet; language practice was performed.
*Ok, a couple of problems, but let's focus on the big one right now.
**Yes, I know Dremel™ is a trademarked name and you're supposed to say 'rotary tool' unless it's theirs; hell with that, I've always called them 'dremel tools'. If Dremel™ wants to bitch at me about it, well, if that's the worst problem I have...