Glenn,
The problem with graphite powder is that it's dirty black stuff that can end up in a mess - lead pencils are made of graphite (well, they were back in the old days). Image pencil lead powder all over the place
.
I use graphite powder in door lock key holes - it's good slippery stuff (hence the above reference to a locksmiths for some).
I had very stiff window winders in my everyday car and, like
fcfromscratch, use silicone lubricant (spray can from most car parts places) liberally on the channels. Now they do up & down like a dream. Give the channels a bloody good squirt before you install them.
Martin