RetroClean. I am not in any way connected to the company. I used it on my great-grandmother's quilts which hadn't been cleaned for a good long time. The directions were easy to follow and the water with the RetroClean was used for more than one quilt. I used a large plastic bin and put it outside so the heat from the sun would do its magic.
Whatever you choose, good luck.
P.S. Snow will have particles of 'junk' in it from the environment. Depending on where you live it could leave residual
dirt that is worse than what's already in it.