"...Well I made it at 0% and it's hard as a rock and now in the cupboard to cure...."
Neve -- If you're wanting to make a dry powder laundry soap, I'd grate the soap NOW while it is as fresh as possible. If you let it dry out, even for a few days, it will be a serious chore if you're grating by hand.
If you also want to turn the soap into a fine, faster-dissolving powder (best for cold water loads or HE machines), you also want to work with fresh soap for the best results. I don't know how to manage this if working only with hand tools -- I use a food processor. First, I grate all of the soap with the grating blade. I do small batches so the soap doesn't pack into the processor bowl. I want the soap in the bowl to stay as loose, fluffy, and cool as possible. I spread the grated soap into a large pan as I work, so it can cool off more and remain loose and fluffy.
When all is grated, I switch over to the sharp chopping/mixing blade. For every batch, I put a handful of grated soap and a handful of one of your powders (the washing soda, for example) into the processor bowl and process until the whole thing is a fairly fine powder. The largest particles should be no more than about 1/16" (1 mm) across. I process about 30-40 seconds per batch.
Tip: If the soap mixture starts to get too warm in the processor bowl, it will clump up, not break down. To solve that problem, use less soap and more powder per batch. The soap must stay loose and powdery to break down properly.
Tip: Don't make the batches too large or the processor won't break the soap up fine enough. (Found that out the hard way.)