Yes you can use a lube plate - in fact, Reese makes and sells them themselves.
Below is an excerpt from the From the Reese Products web site - Support area Lot's of good infor there for new hitch owners - go to the Reese site and click Support. Reese Products
What kind of maintenance needs to be done to the 5th Wheel Hitch?
1. Lubricate skid plate surface of the hitch with automotive type chassis grease or use a plastic lube plate to provide a lubricated surface. Use white lithium spray lube or engine oil to lubricate pivot points of moving parts within the hitch.
2. Plastic lube plates (Reese No. 74295) can be used to avoid messy grease. The plastic lube plate must not exceed 3/16 of an inch in thickness to ensure hitch will operate properly. Lube plates must be 10 inches in diameter or larger to properly distribute king pin weight.
3. Before each trip or maneuver, operate the handle and check that the jaws open and close freely.
4. See that all hitch pull pins are in place and the spring retaining pins are installed.
5. Recheck tightness of all hardware every 1000 miles of use.
6. Lubrication to the hitch is essential to provide for a good long service life. Any pivoting point inside the head should be lubricated with a white lithium spray lube. The pivoting points outside the head need to be lubricated with a high pressure lube, such as 80/90 gear lube or grease. Reese offers the high pressure lube as (PN 52250). This will allow for easier operation of the hitch. The skid plate can use either grease or a minimum of a 10" lube plate (PN 74295). When lubricating you should always remove the old lubricant to remove any road grim that has collected to prevent excessive wearing of components. All hardware should be inspected and torqued periodically per the recommended torque specification in the instruction manual.