Whatever you use, DON'T use anything with Acetone in it as it may discolor the Bluing.
Back in the Day I used Stoddard Solvent, Ballistol, or WD-40 to remove Cosmoline from DCM/CMP M1-Garands, Springfields, and other Surplus Rifles.
You could use standard Automotive Brake Cleaner, so long as it has no Acetone in it.
Electrical Connector Cleaner also works and don't use it if it has Silicone in it.