SweatVac is what I use, but a Halo, the PI skull cap, even a dew rag or anything else probably works just as well. I like the full head covering though as before I started using the SweatVac my scalp was getting tanned in the pattern of the holes in my helmet. I found that I was actually cooler with the full head covering too.
It looks stupid, but it seems to help if the front edge of it is pulled right down to the eyebrows. Also it seems that riding with glasses that have a narrow height to them seems to also help. Maybe that promotes better airflow to aid in evaporation of the sweat instead of big wide lenses blocking the airflow.