Open the vents to the cargo area to pressurize it, drive with the doors and windows closed, open the vent by drivers side foot to pressurize the cab, have a fan installed and blowing at all times. This all greatly helps reduce the amount of dust that gets in the truck.
My route is 200+ miles of mostly dirt and gravel roads and the amount of dust that gets in my truck is very minimal now that I started doing the above things.