How much the fleece will yield depends on a lot of things such as how lanolin, VM, dirt are in the fleece.
With my first fleece, I wanted to save as much as possible, but now I skirt the heck out of it. Skirting is when you remove the nasty wool around the edges, especially the neck, belly & britchen area.
Then I go through every single lock of the fleece. Gently pull the locks apart, remove any 2nd (short) cuts. Shake the locks. This helps remove a lot of the VM and helps the wool get cleaner faster during the scouring.
This is also a great time to sort the fleece for texture or lock length.
When I actually wash the fleece, I use the washing machine. Fill it up with hot water. I'll put a large stock pot of near boiling water in there also. I use about 3 times the amount of detergent as when I do regular wash.
When the washer has filled, TURN IT OFF!!! Press the fleece into the washer (some folks will put the fleece loosely in a few mesh bags). I figure I wash about 2 lb at a time. MAKE SURE THE WASHER IS OFF!
let it soak for 30 minutes or so. Turn the washer to SPIN (not spin & rinse!) You don't want any water spraying on to the fleece.
When the spin cycle is finished, remove the fleece and examine. You may have to open up the locks some more, especially the tips, if you didn't do this when skirting.
Repeat until you are satisfied that the fleece is clean, fill the washer with hot water and white vinegar to remove any detergent.
Lay it out to dry. flip often
Just remember, the more VM you get out before you scour the fleece, the less you'll have to pick out later.
You can spin it from the lock, or carded.