My comment is more about keeping flies out than getting rid of them once they're inside. I live in the country, on a farm, with 5 turkey houses behind me, and when the houses are empty, we have to deal with a LOT of flies that migrate to our house. One trick I found that helps to keep them out is to hang a plastic bag of water near the door. It doesn't stop all of the flies from coming in but it sure does help.
There are some good ideas here http://www.hometalk.com/diy/outdoor/pest-repeller/q-how-to-get-rid-of-house-fly-8674162
There's a Ziploc bag filled with pennies and water idea over there that sounds fascinating!
Is there anything to get rid of house flies?
www.wikihow.com/Get-Rid-of-Flies-in-the-House
all you need is simple vinegar!
My comment is more about keeping flies out than getting rid of them once they're inside. I live in the country, on a farm, with 5 turkey houses behind me, and when the houses are empty, we have to deal with a LOT of flies that migrate to our house. One trick I found that helps to keep them out is to hang a plastic bag of water near the door. It doesn't stop all of the flies from coming in but it sure does help.
hang fly strips purchased at Menard's or Home Depot (stores like that)
Here is a post I wrote that might help you https://chascrazycreations.com/irish-spring-soap-and-flies/