[Boatanchors] how to lube a roller inductor?

[W2HX]

Hi all,

I've been working on an automatic/motorized antenna coupler (the transmitter
uses tubes and weighs 200 lbs! definitely a boatanchor).  

There is a gigundo roller inductor that makes a loud squealing sounds as it
tunes. I am sure some kind of lubrication would fix this. 

There seem to be 3 points that could be the source of the squealing.  The
front bearing (that holds the shaft), the rear bearing, and then the rod
that the roller rides on from front to back.

How does one properly lubricate a roller inductor? I was afraid that 3 in 1
oil might have a detrimental effect on the conductivity of this.  And I
don't want any arcing.

What's the right way?

Thanks
Eugene