Cleaning cosmo from an M9 sheath

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Forum newbie here, and I've just picked up a LanCay M9 from over on arfcom.

It's got plenty of cosmoline on the blade and inside the sheath, and I'm wondering about the best way to clean it out.

I usually use mineral spirits, then brake cleaner on milsurp gun parts, but I'm afraid it'll be too aggressive for the plastic and cloth.

Anybody has any suggestions, I'd appreciate it!