I can't say I recommend it, but when I'm riding like that, and if it's safe to do so, I'll leave my right hand on the bars, and hold my left hand out to cover the sun. Looks dumb as all get out, but it does work.
As a safety note, when riding with the sun low on your back, it will completely hide your headlight from oncoming traffic. You are 100% invisible at that point. Not much you can do about it other than weave a bit in your lane to get some lateral motion that traffic might see. I always look for my shadow (the one on the ground, not the one I'm riding) when I'm riding. If it's right in front of me, and strethes down the road, I know people can't see me.
Currently Running Stable:
2010 Honda NT700V
1986 Shadow 700
1986 Honda Trail 110 (Postie Bike)
1987 Honda Rebel 450
1973 Honda Mini Trail 50