AlexEarl, did you router the track for the glass? If so, you may want to router out another so that each pane is traveling it's own channel so that they don't grind against each other. If there's enough room, you could just stick on some furniture felt along the glass. Another option would be to install some glass track/runners. I found this supplier in the UK:
Also, when I built my cages I applied 3 coats of Varathane inside, sanded, then applied a final fourth coat for a smooth finish.