I know I've read a lot of places (here included) that these things work well for cleaning up ponies. I've used the original ones recently on a few of my fixer-uppers and they do seem to help, but I am wondering is the original the only ones its a good idea to use? Or are the other versions of the erasers safe for ponies as well? I don't want to accidentally make things much worse by using the wrong kind of eraser.