You can pick up a grater for next to nothing at a thrift store. Most people won't buy them because it is for their food and who knows where they have been, but for soap they are grate. Get it grate.
I don't remember if anyone here has mentioned this, but I run my grated soap along with some of the borax or soda through the food processor when blending the powder. If you just process the soap you get a glob, but the dry ingredient combined with the soap ends up with a nice fine powder that is easy to blend with the other ingredients. I imagine that a blender in small batches would work the same way.
And I forgot to say .... Yes I use the same processor for food as I do soap. I just wash it up well when I am done. I DO have dedicated equipment for when the soap is uncured.