Every glass shop I've been in used dry graphite if the channels needed any lubrication. If the edges of the glass are done correctly, they shouldn't need any. Also...there used to be channels which were made with a nylon strip in the bottom of the channel with dense pile material on the sides. If you can find this in the right size/style, I'd suggest using it. Makes rolling up/down a treat. Graphite is also good for lock cylinders and mixed with Lubriplate.
I agree with Tim about silicone.
