I know the flies are annoying but I don't think that Aero gard repels flys anyway, just mosquitos etc. I know that mint is a really good repelent for flies. This might sound a bit weird but if you have a mint plant you could put a sprig behind your ear, no one would see if you were wearing a hat, and they may stay away from your face at least.

Apparently mosiquots are attracted to blue??? I'm sure if you look on the net you might find some info on colours that attract insects and good types of clothes to deter mosquitos