These are made from styrofoam eggs, which are already textured. Start by painting the eggs with a thin layer of Elmer's glue. This keeps the spray paint (I used Krylon) from eating away at them too much, but you'll still get a little additional pitting from that.
Once the base color was dry I turned the eggs on their sides and used flat black (also spray) to spritz a little on each end. I found it was easier to get a good effect by holding the can about a foot away from the egg for the black layer.