I ordered the citric acid kit from Caribou Gear when I bought some of their game bags a few years ago. (Great bags by the way). It was just a small packet of powder and a pump bottle that you mix before using. I used it 3X on different hunts, and only used it to keep flies off of the meat while I was deboning at the kill site. I had spread out a lightweight plastic sheet to put the meat to cool, and the flies showed up like vultures. The spray worked well, and I didn't notice any taste on the meat later. On a muzzy elk hunt, I had suggested the spray to the other guys I went with, and one of them bought bulk citris spray (2 lbs.), and when he used it for his elk, it didn't keep the flies off at all.
I've had this kit with me for the last dozen hunts, and used it 3X. Cheap and lightweight insurance and well worth it if needed.