All spinners have their own tips and tricks in this regard.
Here's my version...
After picking the fleece for all of the obvious discard I fill a large tub with HOT water and add a small amount of ORVUS paste. This is an agricultural product and should be used with caution.I'm quite a stickler for wearing gloves (on another topic; I also ALWAYS have a full vapor mask and gloves when dyeing).
My fleece is added to the soap and water. This bath is left for a full day after which I will gently change the water for several repetitions until the bath is clear. The entire wash may take place over a period of two to four days depending upon the fleece. It's a gentle process that I tend to take slowly.
The fleece is transferred to a washing machine and put through a gentle spin cycle in order to speed drying time. I do have a washing machine designated for this task as, over time, lanolin will build up and have issue with any other fabrics that you might like to clean.
I use heavy open (gridded) racks hung over the wash tubs for drying.
