Try using the vacuum cleaner hose to suck them up. You can rid yourself of a lot of flies very quickly that way. A friend of mine did it when his house got full of flies from the door constantly being opened during a party he had. At my last house I had an old fashioned walk up 3rd floor attic. Hundreds of flies would collect around the windows, probably coming in via the ridge vent. I’d bring my shop vac up and in a couple minutes would have them all sucked up.