They tend to gather in swarms up here, so I have adopted the approach of charging them, head down, eyes shut (it hurts when you get one in the eye while wearing contacts) and teeth clenched. Any that are heading straight for you hit off the top of your head, and very few fly with a vertical trajectory, so both mouth and nose escape unmolested.
Still trying to find a method that works for cycling. "Eyes shut" aint good..........