Well, dear readers, I have learned some important things when it comes to washing wool. I'm no expert at this, I'm certainly learning as I go. First off, wait until you have the time to thoroughly inspect your fleece and pick out the worst bits. Yep sheep poop dissolves in water, but only up to a certain point. Full bowel movements would take a heck of a lot of washings to get out.
Also, give your fleece some room. I found that with just half a fleece I had to separate it into two buckets so that the water can get all in and around and between the fibers.
I was told that the poop is the easy part, getting the grease out is harder. Horsefeathers. My fleece is turning snow white, except for where there's big clods of poo still. And I wouldn't mind terribly if a bit of the grease did stick around, it feels lovely when working with the wool.