community of dyers

Cashmere is an animal hair fiber, like wool. It's usually best for animal fibers (other than silk) to use acid dyes, since the high pH of soda ash tends to damage wool. You can use Procion MX type dyes as acid dyes, if you substitute vinegar for soda ash. De's experience with soda ash on cashmere is encouraging, though. I wonder if cashmere is actually more durable than wool. In tests I ran, plain worsted wool was very noticeably fuzzier after exposure to soda ash, but it was not cashmere.

All-purpose dye, such as Rit® brand dye, actually contains acid dye (plus another kind of dye), so it can be used, in theory, with better results than this kind of dye mixture will produce on cotton, but a lot of people write that they get unexpected colors when they use all-purpose dye. PRO Chemical & Dye sells a lot of different acid dyes which are perfect for cashmere and other animal fibers.

Acid dyes are typically used with heat, but there are a couple of recipes which don't use heat, which are especially useful if you don't want to invest in a n expensive non-aluminum dyeing pot (never use a dye pot for food), or if you want to avoid more than a little shrinkage. A particularly interesting approach is settng the dye in the sun in a black garbage bag. Pat Williams provides a PDF of this process on Cold Batch Dyeing of Wool with Reactive Dye , and Pro Chemical & Dye has adapted this for Procion MX type dyes at their page, Garbage Bag Dyeing with Wool using PRO MX Reactive Dyes.