I find that year on year, fly spray is totall ineffctive. Even Raid which used to be good, doesnt work. Im sure the flies are getting an inbuilt immunity from it. Ive gone through tins of the bloomin' stuff this year, none has worked unless Ive been able to get so near to the fly that Ive been able to drown the little bugger. I have more luck swatting them with a tea towel if I get one in the kitchen , plus I have those sticky fly papers hanging down.
I used to have one of those "Red Top" fly catcher thingies that smell like rotting flesh, it did work up to a fashion but you have to have it so far from the house and from animals. It was okay for bluebottles, but the normal house flies still came in, plus you had the stink!!!