Washed in Blood?

I read this in a book by Ron Carlson and Ed Decker. I hope I get it right...

I've always been confused about being washed in the "blood" of the lamb. How can I be white as snow if I am covered in the staining power of blood? I know the blood of Jesus was the ultimate sacrifice and no other will ever have to be made. I know that his blood was the last the Father required and no more need be shed. I know that that is why I don't have to die for my sins. Still... how can I be CLEAN if I'm covered in blood?

At times, a ewe might die giving birth. Then there is a lamb that does not have anyone to feed it. Another ewe WILL NOT take on that lamb because it is not of the same blood. At times, a ewe might give birth to a still-lamb, leaving that ewe with all the motherly instincts but no lamb to be a mommy to. The GROSS, AMAZING PART: a farmer will take the skin off of the dead lamb and place it on the lamb that has no mommy. The farmer will give that lamb that is covered in the dead-skin to the ewe that just lost her baby. NOW the ewe will take on this motherless lamb because it is covered in the blood of her lost baby; it will smell like her blood.

Now I can see that we are washed in the blood of Christ, adopted into the the family of God; we smell like him and are taken care of by the Father.

Eventually, the farmer can take the dead skin away and the mother will be used to the new lamb and treat it like her very own. Even after the blood is washed away and the lamb is clean, the ewe will take care of it the same as if it were of her own blood. WOW! Now I see the metaphor.