Greetings from GEORGIA
IF you have lots of money to burn snake away is great, moth balls would hurt your chickens.
If you want to keep snakes away it is very simple create a good coop that is four sided and a small door off the ground for the birds to hop through.
Beyond that it is just common sense feed the chickens just right so there is no spillage of feed. This will atract the mice/rats which will in turn bring snakes knocking at your door. No mice/rats no snakes if you do get one it is more of luck he happened upon them most snakes do not go after eggs as there first choice, they will little peeps so protect them a snake will not kill what it can not eat unlike it's best friend humans.
I love snakes my self I keep two pythons in my bedroom and the dog, cat, and chickens all stay outside, even the kids lizard is outside. People have trouble with snakes alot of times from over feeding the animals and spilling around the yard which attracts the rodents.
Kill the rodens and you kill the snake problem.