So there's your raw fiber, slumping in its container, possibly glaring at you malevolently, daring you to try to scour it. Dump it out onto clean concrete or an old sheet. If alpaca/llama: separate it into a thin layer, pick out the obvious big stuff, remove handfuls of the very badly contaminated stuff. Fluff it up, while holding your breath. Return to container. If adult wool: unroll the fleece and place it tip upward, sheared side (butt) side down, arrange in a shape the way the sheep grew it. It should be shaped like an animal hide. Now skirt it: go around the outside edges, pulling off anything that looks ugly, dirty, different than the middle. A sheep has "grease locks" in each of its armpits, pull those out. Remove any soiled wool or even slightly discolored wool from the tail area. Check the neck area for rubbed, felted wool, remove that. The belly wool should NOT have even been in your bag. If it is, set it aside. Now, this is your call, the "britch" wool, where a sheep would normally be wearing Levi jeans, is almost always coarser and longer than the rest of the fleece. Separate that from the rest of the fleece if you wish. It can also be processed with the body of the wool if you prefer. Do not DISCARD any of your skirtings, my philosophy is that there is no bad wool, just wool we haven't decided what to do with yet. Set the skirtings aside for later.
Washing the fiber:
1. Hot HOT water, I use a dishwashing basin in a kitchen sink. You will be washing small batches for best results. Fill basin with hottest tap water, even boiling is not too hot. It will not felt or matt the fiber, and you need the heat to melt the lanolin in the wool to combine it with your detergent.
2. Laundry detergent: you need a scouring agent that will not foam up much, because you have to rinse it out and want that to be easy. Laundry detergent is designed not to foam up, unlike things like Dawn dish soap. Consumer Reports magazine published a comparison of laundry detergents, the top two were Tide, and Costco's Kirkland brand, the powdered form of each. To me, Tide reeks. And it's expensive. I use Kirkland, mild citrus odor. Place 1/2 as much as you'd wash a load of laundry with (I use 1/2 scoop) into your hot HOT water, stir to dissolve, around 1 minute. Immerse about 6 oz. of wool or alpaca into the solution, push down, do not stir. Set timer for 15 minutes. It takes wool 12 minutes just to get wet. Any more than 15 and your water gets too cool, will leave the fiber sticky even through repeated hot rinses. Don't let it cool down. I use a basket from the Dollar Tree with a mesh bottom that just fits inside my dish basin, to gently lift the fiber out of the dirty water. Set aside, dump the basin, rinse, then fill with hot HOT water again, and add 1-2 Tablespoons of citric acid, or a small splash of white vinegar to the first rinse. Shake the basket to remove as much dirty water as possible, then dump the fiber into the rinse water. Immerse completely (I use the bottom of the basket to squish it down) then immediately remove fiber from rinse. Repeat rinsing procedure, this time using clear hot HOT water. Set fiber basket aside, do not dump basin, instead add detergent to it and wash the next 6 oz. batch of fiber. Saves on hot water.
3. Spin or whizz wet fiber: place fiber into mesh garment bag and run through spin cycle of washing machine, or tie rope to bag and twirl it around as fast as you can outdoors to remove as much water as you can. Fluff up fiber and lay on a mesh grid to dry, preferably in a breezy place in the sunshine. In mid winter, use a fan. You don't need heat to dry it, you DO need air movement.
4: FOR DYEING: you can take the fiber directly out of the 2nd rinse and put it directly into the hot dye pot, it's hot enough the dye bath won't shock it into felting. Saves time on having to dry it first.
I wash 10 lb. of dirty fiber a day using this method.