Hand shake your blanket regularly and hang to ventilate. Spot clean using 1/3 vinegar 2/3 water
Fill a washing machine with warm water and add a very small amount of mild wool safe or Castile soap(if it suds you are using too much soap). Wash on the short delicate cycle, rinse on cold setting then hang to air dry out of direct sun.
A gentler alternative is to bathe your blanket in a sink of warm water with a scant amount of wool safe soap. Soaking allows the dirt to come out on its own. Do not scrub or agitate, which can damage the fibres and possibly affect a blanket shape. Roll in a towel several times to get the water out and hang to dry out of the sun. Never use hot water of regular soap, this could felt your blanket.
Wash wool blankets before storing and store wool in a cedar chest or sealed plastic bag with sachets of any combination of peppermint, lavender, cloves, cinnamon, thyme, rosemary, ginger or citronella. Wool blankets that are used regularly are less prone to moths, which like dark undisturbed locations.