Generally, its best to leave the portion that inserts into the bushings bare/polished with a light coating of grease.
The rest gets primed and painted.
A common glider practice is took keep them lightly greased - wiped down and new grease every insertion - and stored in a sealed zip-lock baggie when out of the plane.
I learned a trick you might want to consider. Spray the tool with a dry graphite, say three coats and then burnish it with a shop rag. Do this a couple of times and what you end up with is a nice coating on the metal that won't chip off and is not a film coating. The graphite works into the grain of the metal so it doesn't change it's dimensions.
Works good,last long time. http://www.aircraftspruce.com/catalog/cspages/drygraphite5200.php
