Just grating the soap works well. It desolves in water
when you do your washing
... so creating a fine powder or anything like that doesn't really help the purpose of it.
I'll just add, this soap is, at the very minimum, as effective as any basic off-the-shelf laundry
powders. Minus the smellgood stuff... I've been using it for around 2 years now, and the only time I need extra cleaning
power is to get stains out and occasionally whiten the whites. Which, in my experience, is exactly the same as store bought soaps. You can also add smellgoods and softeners as you wish (and there are organic methods of both)
It's not meant to compete with high-tech, high-priced soaps. If that's your thing, you probably won't like it.