I use buff or tan in an airbrush.
A cheap and quick dust method is to use talcum powder. Drug stores sell various flesh tone powders and most of the colors make good dust. It can be dusted on. One method is to hold a fine screen over the model, dip a brush in some of the talcum, and brush the screen. The talcum will fall through the screen in a dusty cloud.
I tip the car up at different angles so I get more on the bottom of the sides, nose, and tail, then a very gingerly application on top. I also use a brush to actually brush the stuff on tires, then brush it around and brush excess off. This works on vinyl or rubber tires, when paint does not.