Since you don't mention the model of your trailer but have a "toothed rail" I will assume you have a mechanical slide. What you are doing is what the manufacturer recommends. Cleaning off road grime and spraying with dry silicone lube will keep dust from sticking. If you go to the manufacturers website (most likely Lippert) you can download the manual for your slide.
Hank & Lynn
2007 Cougar 290RKS, E-Z Flex, 16" XPS RIBs ( SOLD
.. Gonna miss her ... looking for new 5r)
2004.5 Dodge 2500 QC, LB, 5.9HO, WestTach gauges, Ride-Rite