Hey SP I had a look at your blog and I just wanted to warn you that you should not eat soap. Some of your soaps look delicious!!!
I've been searching the web and most often they say about 1/2 C. per pound although one page said 1/4 C. per pound.
My favorite book ("Essentially Soap" by Dr. Robert S. McDaniel) says start out with 1/2 C. per pound grated soap, heat and occasionally stir 1-2 hours, and add up to another 1/2 C. if necessary. He says if it's lumpy to use a stick blender to smooth it out.
Another book ("Soapmaking for Fun & Profit" by Maria Given Nerius) says use 12 oz. per pound of soap.
I hope to figure out rebatching too. I like that you can forget about lye ruining your scenting and coloring.