So, here's a good description from PureCollection on how to hand wash cashmere:
For hand washing: Soak the sweater in sudsy, lukewarm water for 5 minutes, then gently ‘squish’ to let the suds soak through the fibres. Rinse in lukewarm water using the same ‘squishing’ action – never wringing - until the water is clear. Roll the garment in a towel to remove the extra moisture and speed drying.
As far as drying and re-shaping, I like Martha Stewart's instructions (you can find them in my earlier post). And if you need a little starter kit to take care of your cashmere, I sell one in my online shop - it includes Eucalan samples, a defuzzer comb and some Moth-Away herbal sachets.
I wash all of the cashmere sweaters I receive in the washing machine (I have a front loader HD) with warm water and dry them in the dryer on "normal". I can tell you that most of the sweaters shrink at least a little bit - but not one has ever shrunk to the point of being felted. (I have my own opinion about whether cashmere will felt or not). I also wash my personal cashmere sweaters in the washing machine (I'm too lazy to hand wash) on the gentle cycle, cold water and then hang them to dry. Then, once they are 100% dry, I throw them in a warm dryer to fluff them up. If they need blocking or reshaping, I do it afterward with the iron on steam setting. That's just what I do. If I were you, I would follow the experts advice and do as I say and not as I do. But that's just if I were you, and I'm not. You decide.