Yeah, secondhand’s the best! I’ve had really good luck searching for Madewell and Everlane cashmere sweaters that I didn’t buy new but admired and had saved on Pinterest. I usually just do a good soak in something like Dr. Bronner’s or a gentle dish soap when I first get it! Lots of soap, cold water; rinse a few times, gently (very gently!) squeezing, without wringing it, until the water runs clear. Then hang-dry on a drying rack with a towel placed underneath it, to make sure it doesn’t get stretched by its own weight.