So I tried to make a few 3d asteroids. For my first attempt, I used dropzone flight bases and pink foam.
First I outlined the foam with asteroid shapes from the official templates. Then I cut out the asteroids and gave them a little shaping and texture. Then I sprayed them with black spraypaint which ate into the foam and gave even more texture. Following that was a few layers of brushed and drybrushed blacks and grays.