Do not use it at all if your soils are not selenium-deficient. Ask the county agent or state agricultural college if you are not sure. A general guideline is that the entire east coast is selenium-deficient and the west had abundant selenium. Hand spinners do not like to pick hay heads and burrs out of their fiber and will not buy from you if your goats get into the cockleburs. Simple dirt will wash out in the scouring.
Some fleeces look terrible in the grease but wash up beautifully.
Lice are also a contaminant. Apart from endangering the life of your goats, lice ruin the fleece with nits, which cannot be removed easily. Hand spinners will not buy fleeces full of nits, no matter how soft or beautifully colored. Keep this in mind when you are tempted to scrimp on pour-on wormer. Conclusion Angora goats are the most difficult goats to raise, they need more food and shelter to thrive than other breeds.