Washing the fleece requires buckets of hot water. The water should be about 120 degrees but the quick way to judge is if it is too hot to put your hands in it without gloves, it’s hot enough. You don’t want it much over 120 as the wool will start to cook.
I have heard of several opinions on soap, but one mill owner told me to use the cheapest of laundry detergent and about 3 times the amount called for. This is mixed in one bucket and the wool gently pressed into the water. Then it’s allowed to soak for no more than 20 minutes. Agitating the fleece in hot water will cause it to felt, so handled gently and wear gloves. When you remove the fleece, squeeze it gently and place it in the next bucket or sink.
If the fleece is dirty, you can wash it two or even three times. Always try to match the temperature of the water so that the fleece doesn’t become felted. When you’re ready to rinse, just use clear hot water and soak again. Repeat until the water runs clear. You can spin the fleece in a laundry bag, spin in a washing machine (Don’t let it agitate) or roll in a towel and squeeze to remove excess water. Spread on something like a screen to let it dry.