We just bought some horse fly spray for keeping the flies and mosquitos away, it seems to be working well. We have a horrible mosquito population since we live on wetlands. I HATE mosquitos and so do the goats. The vet also told me that Frontline flea spray works.
I use Endure its made for horses and is safe even for foals...seems to work ok...on horses it lasts for 10 days but it doesn't seem to be effective for that long on the goats.
We have been using just the Bronco brand equine fly spray on our goats and it seems to be working well doesnt last forever though usually have to use it about every coupla days or so. Ive also heard that sprinkling 7 dust on them works also, havent tried that though.