Robert, it's the same as the stuff you probably used in grade school. Here's the stuff I use. Very reasonable priced as you can see from the $1.99 price tag and the size comparison to a MM jar.
It wipes off with water so I use damp paper towel pieces to wipe it off. The trick is the dampness of the paper towels. A little too wet and it takes it all off and too dry and it doesn't work.