Bluing is essentially a controlled and refined rust.
It looks nice. By itself,it offers no rust protection. What it does is offer a bit of"tooth" for oil or other protective film to anchor to. Like paint primer.
I don't know if this is the "approved" professional gunsmith method,but I get beeswax to reluctantly almost dissolve in turpentine.
When I get done with a boiling water/rust blue job I seal the fresh blue with the beeswax solution,then wipe it down.
Certainly the harsh solvents like carb or brake cleaner will degrease...but by stripping the blue of whatever oil,or rust inhibitive film (like RIG) the micro texture of the blue is holding,you remove any corrosion protection you may have had.
Have you ever used a well seasoned black cast iron frying pan? You can cook eggs in it just as non-stick as a Teflon pan.
Take that same pan and degrease it with harsh dishwashing and it will rust,and your eggs and pabcakes will stick.
These days,we recognize petroleum products on the skin are not good for you,bt long ago it was common and effective to use clean motor oil to cut the black nasty dirt off your hands when mechanicing.
I don't know what you are trying to clean...I guess revolver cylinders,etc get carboned up,but for most blues exterior surfaces,a wipe down with a lightly oiled rag or a "RIG rag" is all that's necessary.
There are 100 year old guns that are still pristine .They had no magic de-greasers. They may have used whale oil,or deer tallow,or Vaseline.
Any salt free barrier to water and oxygen mght do.
Keep that cast iron frying pan in mind
