Wait until they get really dense and then attack samurai style with a flyswatter. This works best in a small space like a bathroom.
If you can’t get 5 aerial kills in 5 strokes you’re not an Ace. So keep practicing until you *are *an Ace. Believe me when I say it’s both doable and way more satisfying than it ought to be.
We outweigh them 100,000 to one. We ought to be able to kill them by hand with ease. And yet there they are, buzzing around taunting us or even just sitting there with that smug look on their tiny filthy face.
Five at a time; it feels so good. Try it; you’ll be hooked.
8 cats? I’m guessing one of them left you a present under the TV set and the flies had a banquet.
Flies are attracted to light, so one possibility is to get one of the led bug zapper things (looks like a big fat light bulb) and turn it on in an otherwise dark room.