Hi All,  Here in the UK I briefly experimented with powdered graphite
but found it a waste of time.  In the early 1970's I discovered
colloidal graphite in alcohol made by Rocol.  It's readily available
from Kimber Allen Organ supplies here in the UK.  We used this material
to coat the sliders in soundboards and just about anywhere else there
was light friction.  I found that one coat on the slider valves of any
roll drive would endure for many years.  It is of course important to
ensure that the friction surfaces are flat and grease free.

Cheers for now (I'm in the middle of a Renal Colic Attack)
Paul Camps