I have had luck with using White out for correcting spellng mistakes on paper. It has the applicator brush and covers in one application. The sun will never fade it. But it is tricky to do, and requires a steady hand. But the downside will be that since the buttons are illuminated through the white part you will no longer see the illumination as the white out does block that out. DCO
I have a set of artist brushes and they are graduated in size from about 1/2 wide down to a short tiny brush with just a few tiny strands. I was able to touch up mine a little with it but it takes a steady hand and the ability to see, and I have neither. I supposed you could smear it and when it dries lightly sand it with very very fine sandpaper to remove the extra from the area around the writing.