You should only handwash snowwear.  For those very dirty spots, please handle them smoothly and do handwash.

For laundry detergent, it will be the best to use special detergent for washing snowwears.  If not, use a neutral detergent(laundry soap or regular powder detergent).  You should never use some sort of chlorine bleaches.  When handwashing, please do not rub them as it will take off its coating, rather gently press them to wash away dirts.  YOU SHOULD NEVER leave them under water for more than 20 minutes.  

After handwashing, hang them in well-ventilated shade place to dry them.  

After drying, if you use a water-repellent spray such as "Toko Textile Proof', your ROMP snowwear will last long well.  :)