Mazda OEM window guide bushings eventually break down and gunk up with old lubricant. Replacing them with more durable and slippery delrin parts brings windows back to a smooth glide.
Do not over-tighten the screw and risk breaking the glass. I had to sand the bottoms of the bushings a little bit shorter so that they could spin freely with the screws tightened.
Supposedly Honda Shin-Etsu silicone grease is the best for this, but I just used Super Lube from the hardware store.
2021 Update: Use thin white lithium or silicone spray, thick grease will collect dirt and grime and become sludge over time. It’s much easier to reapply a thin spray.