Thanks for the detailed info, the instructions are great. I decided to perform this today while I had my wife's bike torn apart for multiple maintenance items. I discovered the sliders had compressed just a bit at the points where the internal nut is located which was dragging just a bit at the points where the welds are located along the track.
Also, there was evidence of slight twisting of the square nuts in the sliders by the wear patterns on the corners of the nuts (probably happened when originally tightened) and slight rubbing against the sides of the track. Additionally, the lubricant was gummy, which was also causing some additional friction. Fortunately, the gear and cables were in good shape. I dressed up the sliders, and dry-fitted all the components and all was sliding free and easy. I re-greased all the pertinent points and reassembled.
However, when I reassembled the sliders, I tightened the bolts and found the assembly was still dragging just a bit at the weld points. I backed the bolts off just slightly which immediately relieved the dragging at the weld points (which either un-twisted the nuts, or uncompressed the plastic slider). The assembly is now as smooth as glass. Now, just one more assembly to go...