While I have not used Hedge Apples, sounds like it is worth a try. I do know that if you gather green walnuts, once they form, it will drive out most insects...very pungent smell to them.
Realistically, the solution is to kill the food source. Get some insect killer at the Depot and mix it up in a sprayer and spray the baseboards around the barn. Once you kill the food source the spiders should go away...unless you live by a lake or place that breeds the flying types then you won't be able to cut of the food source. If the later is true, might try and tie up some bundles of moth balls in several places and see how that works....they work great for smaller areas but not sure how it would work in a big area like that.