There is nothing available that will give the luster and depth of a nice high polish blue finish. There are some satin black finishes available (such as our Roguard) but frankly they cannot duplicate the appearance of bluing.
Bluing is a type of black oxide finish, it is what is considered a conversion process rather than a coating or plating. As such, the blue/black finish is extremely thin; if you were to measure a steel part - even to .0001" - before and after bluing you would not be able to measure any dimensional change. All a long-winded way of saying that bluing is very thin and wears through pretty quickly.
Unfortunately there is no way to protect a blued firearm that is used & carried from showing wear over time. You can minimize the wear by using a properly fitted, good quality holster and not using abrasive cleaning products like lead removal cloths. The only "trick" I've heard is to apply a paste wax to the surface, but that would be more for corrosion resistance than protection from wear in my opinion.
The Robar Companies
Offering premium firearm finishes, custom gunsmithing and polymer pistol frame reductions & modifications since 1986.