I swear I saw a post (by Grant?) on here somewhere showing the use of fine ballast under the track work. I had some crusher run out back as that's all I could get my hands on. I was so impressed by the picture that I've been screening ballast getting rid of the large stuff. My girl thinks I'm nuts. I have to do it right!

 

Now that is attention to detail hehe  Post pics of the result when you get all done.

Engineer Joe, my method of laying track is to remove the sod 10 inches wide where the track will lay. Then fill and tamp the 2 to 3 inch trench in with decomposed granite(I get mine at Home Depot in 50 pound bags or delivered from materials yard by the ton) to about an inch above ground level. Then I lay the track and use Red Cross Pigeon Grit(I get it at the feed store) spread between and alongside the ties as ballast to hold the track.  

I found that 1/8inch stone ( called Rice stone) works the best for me!