I bought a can of spray white lithium grease, and with the little tube I can put it where I want (but it still makes a mess).
Note what he says about never removing the lowest roller because that is where the spring is attached via a cable. He shows how to replace the lowest roller while leaving the cable attached by bending the track.My rollers are plain plastic with no bearing, so I should buy a set of 10 rollers -- he suggests getting the 10 pack of "Z-bearing" rollers -- exactly how many I need. Mine have a 4 inch shaft.
These are $40 plus $7.52 shipping.Tom's Home repair pages / tom@mmto.org