I have a YUGO surplus SKS that is really icky. Still has the cosmoline all over it.
Took me forever to clean the cosmoline off my Yugo SKS. Lots of paint thinner, steel wool, soaking parts in thinner, cleaning stock slots with a condenser brush. Then clean the wood some more when it weeps cosmoline.
But there’s a fine rifle under all that goo. Don’t forget to oil it before firing.