The thing is, if I start on one wall, I have to do the next, because it suddenly looks like someone pissed all over it in comparison to the shiny, clean wall. >.< And these things dissolve pretty quickly. One big wall ate three erasers, one side of the stairway has so far consumed two and a half.
According to Wikipedia, they're actually really abrasive, they just feel soft because they're abrasive in a tiny way. :D ... um, maybe I should wear gloves when I use them.