If you have a pitted area and the plan is to remove it to clean steel, then files are OK, They just remove metal fasted than abrasive papers.. Same idea as rough cut files remove fasted than fine cut files.

You don't really need to 'draw file' the area.
You need to file it carefully from different directions in order to avoid a depression that is easily seen when you are done and the pits are gone.
You have to blend the are in with the surrounding area of undisturbed metal/finish.
Once you are done with files, you move to abrasive papers or cloth.
Start with something like 180 and go up to whatever you need to bring the polish to match the orig surrounding finish.
Polish at opposing angles to the grit you just polished. That will allow you to see the coarser grit (lines) being cut away. Don't worry about the final direction of the grit lines till you reach the final grit. They will take care of themselves at that point if you have removed all the coarser lines up to that point.
If not, those older, coarser lines will be staring at you like someone just keyed your car door.

You need to bring the filed/polished area out of the immediate pitted area and taper it into the metal that has no blemishes in it.
The more you taper and blend the repair into the surrounding area, the less the repair will be noticable.
The downside is that you will be removing perfectly good finish as you bring that gentle taper outward from the divot you created by removing the pitting.

Once blended in to your satisfaction, now you have to polish the 'in the white' are you have created to match the polish that is UNDER the bluing on the rest of the metal.
Look closely at the orig finish. Not finger smears of oil but the orig polishing grit lines. Follow those grit lines off of the orig surface and on to your in the white newly polished surface. Bring up the brilliance of the polish on your new surface to match the orig.

Now reblue the new surface.
Chemical cold blues can work pretty good. But results are usually lacking in the end.
The spot that is prepared will show and the more you work it over, the worse it'll look generally.
Rustblue can blend quite well.
Quick (Express) Rust works very well in touching up spots like this. Slow rust can be used but you have to watch for the soln etching and leaving an matted finish in that area. It takes some experience and technique.
A Hot Salt dunk will usually match quite well.
But that would require the bbl being removed & re-installed.

Lots of options.
Another is to clear the gun of oil.
Boil the bbl portion of the assembled (bbl & frame) in plain water. That'll turn any rust to blue/black oxide just as if rust bluing.
The fine dusty stuff will card right off with steel wool (de-oiled). It will NOT remove pitting but will kill the rust and turn existing rust blu/black and leave a better looking finish than any rust on the surface.

I have a Win21 here now that has a few light patches of pitting and most of the blue gone on the bottom of the frame . The top of the frame & top lever was pitted.
I polished the bottom of the frame out, left the sides untouched except for a light 1200grit hand polish.
Then filed the top of the frame and the edges of the standing breechs, Then polished them back down to 1000 grit.

I will rust blue the entire action and parts to blend the old orig blue and polish on the sides in to the new polish on the top and bottom.

Kind of the same idea on a larger scale. Trying to save the orig polish and finish where I can. My idea of restoration.
Not the easiest or quickest,,but restoration as I see it.