Wool felt is a pure natural material which is water- and stain repellent and does not require frequent washing. Just expose your felt garment to fresh air from time to time to clean and refresh. Small items can easily be washed by hand with a mild soap in lukewarm water, avoid too much rubbing. After rinsing, spin or pre-dry in a towel, stretch and re-shape when damp and then air dry. 3d forms will be permanent and elastic again after drying.
Don’t use a tumble dryer, as excessive heat and agitation may cause further shrinking.
Large garments or objects should rather be dry cleaned.
For storing felt, use well-sealed bags and add moth protection.