Riding, and laying out, grass tracks can be a ton of fun. Especially, when you have someone else of equal riding ability to race on it against.
Riding them by yourself is a good way to learn advanced turning techniques for non rutted, non bermed turns.
Get some cones and buckets and put them in places to mark the turns. These work well because they are easily moved when you want to change the nature or severity of the turns.
One you have your track worn in, you may want to use more permanent markings like stakes, ribbon or hay bales or whatever else you have. If you have a lot of trees, you can rake leaves and put them in a 55 gal plastic trash bag to make some soft course markers.