With an auto slide hitch the plate and head moves with the kingpin, so lubrication of the plate is not necessary and some teflon plates will raise the kingpin enough so that the hitch will bind (on an auto slider)- so no lube needed on the hitch plate and kingpin, but lube is needed on the sliding portion of the hitch, see the manufacturers recommendations.
On my slider I can see marks from hooking and unhooking and a bit of scratching from the little bit of movement - after 5,000 miles or so.
On my Reese manual-slider I used a teflon plate and judicious applications of a spray lube.
Tim