I dunno how effective DEET is after being out in the open. But you can always but a bottle of the industrial stuff DEET, 50%, completely soak a bounty towel in it. Then bag it in 2 zip loc bags. If the time comes, whip it out and wipe yourself with it. If the fly situation's that bad, you'll put up with the poison on you for a while. Don't forget to bring a few packets of sanitary wipes to wipe yourself and your hands down afterwards.