The asphalt presented a problem, big gaps in places because of the way they are made. I used my little white rocks from the train days. I spray painted them inside of a box and then shook it up. This took several applications and then used spray adhesive to hold them down. After a few more apps of black paint, and then spraying down the shingles, it blended well enough and looked real enough for me. On a side note, open your garage door when you spray paint inside of it. Trust me, do not skip that part.
