How I wash Fleece
I use my top loading washing machine, because of the ease of using the spin cycle to remove excess water at each stage of the process. However, you can use a tub or bath. If you do not have access to a spin cycle gently press excess water out, but do not wring the wool.
Always remove wool from the machine while filling with water.
Never agitate or tumble wool, unless you are wanting to make felt.
Water temperature. It is important to use hot water to dissolve the grease. Such hot water is not necessary during rinsing stages, but my rule of thumb is never put the wool into water colder than the wool is, because this will encourage the felting process.
Place fleece loosely in open meshed bags (I use onion sacks). I use at least two bags so that I can balance the washing machine on the spin cycle.
Soak in cold water (typically overnight) so wool is well wetted and dirt is loosened. This water is excellent for watering plants if you want to bail it out. Drain, spin and remove wool bags.
Fill machine with hot water and add detergent or well dissolved soap flakes. I have used fancy wool detergents and find them useful for fleeces with a high wax component in the grease (such as Merino) and dirty fleeces. However, they are not necessary for most of my fleeces, and I typically use much cheaper dish washing liquid – about a cupful. Place the wool bags in the soapy water and gently prod to ensure unimpeded penetration of the water to the center of the bags. (This is why the wool should be loose in the bags). Soak about 15 minutes. Do not let the water cool too much, because dissolved grease and dirt can start depositing back onto the wool. Drain, spin and remove bags.
Without removing the wool from the bags, check it especially a few of the tips. If the fleece is particularly dirty or greasy step 3 may need to be repeated.
Fill the machine with hot water, add the wool bags, gently prod to ensure good water penetration to the center of the bags and soak for a few minutes. Drain, spin and remove wool bags.
Repeat step 4 at least twice, and more if necessary, until rinse water is clear. Thorough rinsing is important to get a nice clean fleece. But also be on the look out for incipient felting. It would be better to work with a less clean fleece than ruin it altogether.
When fleece is rinsed, gently remove it from the bags and spread out to dry. Drying is most effective if air can circulate through from underneath. I typically spread the wet wool on lengths of curtain net laid out on my slatted sundeck. If it looks like rain I just roll up the wool in the net and bring inside. Later, it is easy to take outside again, and unroll to continue drying.