You can put the drain plug in a sink, fill the sink with cold water, and mix in the manufacturers recommended amount of Woolite. Then add the cashmere garment and swish it gently in the sink. Let it soak for around twenty minutes. Drain the sink and rinse. Roll in a towel, reshape and lay flat to dry.
Fill your sink with cool water and mild laundry soap. Submerge cashmere item and allow to soak for 30 minutes. Rinse thoroughly with cool water making sure all detergent is removed. Press the water out and allow garment to lie flat until completely dry. Low iron if needed.
I would recommend that you let the dry cleaners clean the cashmere for you that way if anything happens to it then they are responsible and can buy you a new one.
Because cashmere is a delicate material, it should not be cleaned at home using products typically used for other types of laundry. The best way to clean cashmere is to have it dry cleaned.
Hand was with extreme care in a sink, with a product like "Woolite". Don't let it soak. Rinse once and then again, adding a little fabric softener. Let the water out and let the garment drain for about five minutes. Gently coax excess water out and roll up in a clean towel. Dry flat.