Do you mean real sheepskin, and sheepskin sized?
I understand they are washable BUT do NOT use detergent. Get some soap flakes. If you don't mind risking suds everywhere, you can use a machine. It helps to shake/knock the worst of the bits off it before you start. Use hair conditioner instead of fabric conditioner at the end. Hang it out to dry. You will have to brush/comb the fleece to make it go fluffy again and you do risk pulling some of the wool off it when you do this, so be gentle.