Good question Stude. It's Gator brand waterproof sandpaper from Ace Hardware. The abrasive is Silicon Carbide, not Emery. My bad. Back when I was a kid we called any such paper used for metal sanding Emery paper. I never got out of the habit.

I don't think a dowel would add to the effectiveness. The rolled tube is plenty stiff enough, and you don't want to apply a lot of pressure anyway. A light touch and holding the angle is all it takes.