I know of two products that would probably work to make a tracker bar
more slippery.  Ordinary hard furniture paste wax is used often on metal
parts to make them slide.  I use it on my Shopsmith woodworking machine.
It forms a good hard surface that takes lots of abuse.  You can probably
even try automobile paste wax.

Another thought for the more "high-tech" is a product used for coating
the surface of woodworking table saws.  It comes in a spray can and makes
the surface slippery without imparting anything bad on the wood.

Ed Gloeggler

 [ Polish the brass first.  That rusty-looking color may be brass, too!
 [ -- Robbie