Gleaming isn't a panacea, and in my opinion it doesn't mean track cleaning will be unnecessary thereafter.
In my opinion there is far more 'micro-arcing' over fine irregularities in the railhead -- scratches and gouges, including those from use of excessively abrasive 'cleaners', blocks, and scrubbers. The action is to create a tiny plasma and material transfer with each little spark, and to heat some of the metal to where it oxidizes more readily. If there is any oil or dirt present, including that rolled by dirty or spark-affected wheels, the spark may cause a variety of effects in those, too.
The primary purpose of the sanding steps is to get rid of the fine scratches, edges, etc. to true up the surface. Even the fine grits discussed leave these to some degree: burnishing them down is the purpose of that last step, and while you could make and polish a burnisher to 'accurate' rail profile, the washer trick gives most of the necessary surface finish at much less cost and complexity.
Once the gouges are out there is relatively less causation of enough separation and resistance to induce excessive sparks. And there is less tendency for schmutz either to adhere to the comparative polish or to form insulating or rough spots that interfere with conduction from rail to wheel. Preventive cleaning maintenance may then be as simple as running the rough-side-down weighted Masonite around every couple of weeks, or periodically wiping with a process of one's choice.
Some of the rail prep could be done before the track is laid, "on spec" as it were. In cases where track is to be laid on foam or resilient material, and the 'preparer' is impatient, it might actually be better to temporarily put track sections on the equivalent of a surface plate to do the railhead shaping and ensure gouges are out -- but you'd need to take care neither to miss or round over the ends of track segments (unless simulating the effect of low rail joints!
) so at the very least you might want to use the equivalent of a 'false muzzle' if you pre-sand. The last passes to assure true line and surface of the contact-patch lines, and of course the final burnish, should be with the track finish-installed and tested for both rolling and electrical finish.