Gee, i thought chemical blackening had little or no effect on electric connectivity. It's just a film on the metal, right? not a plating, and unless the laws of friction don't apply to N scale just running wheels over and over it after a certain amount of time the blackening just gets worn off -- much like the top of actual steel rails, leaving shiny metal. However, to get shiny railtops on newly-laid track then scrub you must.
The process of leaving new unblackened track shiny on top while darkening the rest of the rail is a whole different problem.