Either spray silicone, or dry graphite powder are the favorite flavors around here...any type of grease in an "open" environment, is gonna pick up dust & other contaminents, & compound the problem.
I like a product called "Jigaloo"...also I am about to try a "dry" lubricant I found in the local hardware, designed for sliding windows & patio doors.
Pop the panels & get into the tracks with a rag folded 2-4 layers thick on a butter knife or something to clean the accumulated gunk out of the channel before lubing.