In the coop we use pine shavings only. We also have a poop board filled with PDZ which collects most of the droppings.
I read on this forum about vanilla repels flies. It was suggested to use those vanilla scented little trees (for cars). I hang those in the coop during the warm-weather months and I don't have flies. Rather that is the reason, who knows!
My pine shavings deep bedding coop floor is dry. Too dry for much composting, thus deep bedding and not deep litter.
It ends up in the outdoor uncovered run about once per year when I replace it. There the decomposition completes.
My coop is very well ventilated.
My coop also has little to no fly, mosquito, or spider issues.
I keep a spray bottle of natural, homemade, non toxic, insect repellent in the coop.
I use it to coat pretty much everything whenever and fairly often.
1 teaspoon dishwashing liquid
1 tablespoon peppermint extract
3 cups of water
Fairly inexpensive and effective.
A spider's sense of taste comes from its feet.
Unlike myself, they do not like peppermint, and I respect but do not like spiders.
This is used as repellent. It is not intended or used for the death of any insect. Just to keep them out of the coop for my benefit.
FYI, most type of flies detest the taste also.