Buy a big stock pot from the thrift store for a couple bucks. Completely strip and any metal parts can go in the pot with boiling water. The cosmoline will literally melt off and float to the surface. boil
Chu wood (Manchurian Catalpa) used on the Chinese SKS and AK is highly resistant to water.
I wouldn't use boiling water on a Chinese sks stock either. But 125° from the tap will make quick work of the cosmoline on Chinese stocks. However, this would be a bad idea with the Birch, Beech and Elm wood stocks used on the European sks variants.