If tip tinner and wire brushing didn't bring your tip back to working condition, and you really need to finish that last connection or two, bust out some fine-grit (600 or more) sandpaper.

If you're at the point where you're sanding your tip, it's time to pick up a new tip.

Gently drag the tip across the surface of a polishing bar or fine-grit sandpaper, following the shape of the tip.

Be sure to evenly abrade the working surface.

Stop as soon as the stubborn oxidation is removed.

Complete another round of tip tinning (Steps 2-4).