lubricating Speedo cable

["McEwen, Art" <Art.McEwen@moh.gov.on.ca>]

While my TR3A gearbox is at the shop I thought I'd take the opportunity to
re-lubricate the speedometer cable in an attempt to correct the Speedo.
It's currently 10-20 mph too high at speed and I'm told that's because of a
lack of graphite in the cable (see question 2).  However I have 2 questions:

1)  How the &^@(^ do I get the graphite stuff through the entire length of
the cable?

2)  How would a lack of lubrication result in a reading higher then actual?
Wouldn't heat/friction reduce the speed the cable spins?