Unlike regular nickel so called electroless nickel is specifically designed not to shine, so this is not a case of rub it with something to shine it up. The gun looks great, and a casual intermitten wipe down with an oil of choice is fine.
For general cleaning I use VERY little solvent ( in most cases I clean my guns dry, meaning no solvent at all ,and it gets the job done just fine) then again I live in a very low humidity area and this may change if I lived in high humidity.
Also I am not OCD with cleaning - knock enough crud off to keep the gun functional and keep trucking.