Plato LEAD FREE Tip Tinner TT-95 is a fast, efficient, and safe means of re-tinning tips.
20g

This thermally-stable compound is residue free and ESD and environmentally safe. A well tinned soldering tip improves operator performance and satisfaction. Plato Tip-Tin provides improved cleaning and re-tinning of highly oxidized soldering iron tips safely and efficiently.

Just wipe the oxidized soldering tip at normal soldering temperature into the tip tinner for a few seconds until the bright tinning surrounds the working end of the tip, then wipe the excess residue on a wet cellulose sponge - its that easy!