I do believe Perseas posted my method on the tips thread. But, seeing that this is your X I would absolutely not use sandpaper. The reason is because trying to blend sandpaper finishes to match would almost be impossible. Especially when the grit from 3M is going to be different than the same grit from another.
On another forum recently, P helped another and told him go touch up the brushed GP with a.very light, very light rub, of course in a circular rotation around the tube.
I would mention that in your case I would lightly just buff or quickly "hit" the spot quickly without the rotation. Just like the King of Kings says, less is better

I would recommend buying the a multi pack of the different colors of Scotchbrite and the same with steel wool. Please take my recommendation of buying or finding a cheap, no good for anyone, worthless, job stealing, breaking child labor laws, Far East ripoff clone tube of some sort to practice and see what the different mediums look like to help with exactly this.
Or leave it and in a week you'll forget about it! Congrats on your first character mark!