I have finished my first two markers as a test. I liked the way they turned out, so I am now starting 6 more.
The idea is simple enough and the details have been posted in the forums at ww.flamesofwar.com.
I took a washer and glued about 6 inches of pipe cleaner to the washer, with the pipe cleaner extending straight up as the washer is resting on the desk. The best way to describe the way the way teh pip cleaner looks is that it should resemble the wire egg holder you get in the PAS egg dying kits for Easter in the States. I then saturated the pipe cleaner with a water / white glue mixture, then dunked it in a mixture of red and yellow (fall) coarse turf. I did not have any clump foliage, but the coarse turf works ok. It won't be as "full" as you would get with clump foliage. I then remove the pipe cleaner and let it rest for a little bit - about 30 minutes. I should state that I do not do the entire length of the cleaner because I need something to hold it with. Then I spray the "marker" with something called wet water. That is just water and dish detergent mixed together. The detergent allows the water to flow easier. Once the marker is damp, I then add more of the water glue mixture and another dunk. Let it stand, then repeat the wet water and the glue step. Let it dry for 24 hours, then airbrush the marker with black. And you now have an explosion marker.
I think I will try several with clump foliage if I ever see clump foliage. But I am in a tournament this weekend and I hope to have 8 markers ready for the table by Saturday.