You might want to pretreat the stains with spray n wash and a soft bristled brush then let em chill for a while before washing. Ideally you want to use the specialty tech wash stuff for that type of fabric, I think you can use powdered also but dissolve it in warm water first, don't sprinkle directly on to the fabric.
Have you seriously never washed your ski pants?
This is a pretty good guide:
https://blisterreview.com/gear-101/how-to-care-for-your-waterproof-outerwear-down-jackets
Blíster has some other articles on tech fabrics and cleaning that should be helpful.