The dosage is a little less than a teaspoon. I just measured from the scoop that I use. I give it to them once a day in their evening feeding, but not always. If I have to go out and don't get home in time to soak beet pulp, then I skip that day. And of course at shows, I usually don't have time for it. But even after 3 or 4 days at a show, they still aren't bothered.
At shows I do fly spray my obstacle and hunter horses because while it keeps the flies from biting them, one or two might still come buzz around and I don't want them to be distracted in any way. My flies at home know better than to try to come around. They are smart, lol.