Flicks when I can afford it (it's a bit expensive) otherwise whatever is on sale at the farm store. For my guys Flicks lasts a couple days before I need to reapply, if they have not been sweating a lot less often than than even. I use it when I am going on vacation so I don't have to worry about the flies and getting someone to spray while I am gone.
I don't usually go for the all natural stuff but I saw the flicks as part of a fly spray test off and it was one of the top three even among the chemical based sprays.
My gelding Thor fidgets when he is around anything chemically smelling and wiggles all over the place when sprayed with chemically smelling fly spray. He never acts out but obviously does not like it at all. The flicks smells very herbal and he does not mind it at all. I like that I can spray it on anything from the horses to me, the cats, dogs, etc. I even got some in my eye once (I am Very accident prone
) and it didn't burn or anything.