Here the screen has been added, along with white glue mixed with water, and spritzed on the screen. The I threw real dirt on it to stick. Base coat was flat black with gray spray paint over it.
Cut a bunch of tire in half, and painted them with craft paints, and added gras from model railroading supplies.
And finally a finished shot of the dio.
Hope this helps you out. If you use dirt, I sifted mine 2-3 times through various size mesh till I got the size I wanted. Also dilute white glue like Elmers 50-59 with water.