I have a couple of wool blankets that I wash in my top loader. I put in the blanket and fill with lukewarm water and mild detergent. Turn off before it agitates and let it disk. Swish up and down several times, soak again. Then set the washer to spin. Refill and follow the same procedure to rinse. I then hang it on two clothes lines, using plenty of clothes pins to distribute the weight. This has worked well and no shrinkage.
For your wool, can you try a small test piece to see how it holds up with regular washing? Maybe a 5-inch square or two and try a couple of methods.