I have a couple of these, and the action of the framing tracks is a bit stiff. Course they were that way new, as I remember. OK to try to lubricate them, and if so, with what? Vacuum Grease?
+1 on paste wax, it leaves no residue to attract dust.
If there is any corrosion on the tracks, try some very fine Scotch Brite to polish the surfaces, either 0000 or 00000 (steel wool equivalent), these are finer than the usual green stuff sold for kitchen pans.