In the past, I've stuck with Pyranha Fly Spray as it was the most effective on our fly population. Since it's oil-based though, I think it contributed to the burned hair that Izzy gets. So for this year's fly season (all nine months of it), I've switched to Equiderma Neem and Aloe Fly Spray. I can't say yet whether it works as well as Pyranha, but it does smell good and since it's water based, I am hoping it will be kinder to his hair. I ordered two new bottles over the weekend to take advantage of Riding Warehouse's gift card promotion.
According to the directions, you can even use it under the saddle which is great because that's the part of Izzy's coat that suffers the most from sweat and sun. Even though I hose him off, the salt in his sweat is still pretty harsh. The product claims that it repairs damaged ends and softens the hair.
I'll keep you posted.