if you polish a swinger is will get dull unless you keep up with it. they were coated with a clear when new. i've wire wheeled one, looked good for awhile, now its oxidized, and dull, doesn't look as good anymore, needs to be gone over to clean up.
i don't care for that huge hole on the top of your swinger. just gonna collect more dirt and crap. grease zerk should have been in the middle of the back of the carrier and drill a 1/2 inch or so hole in the adjuster plate for a grease gun to fit.
any coating you do to an axle will eventually get nicked and chipped. spray can won't last, bare will rust unless you keep up wth it, chrome and nickle will ding and chip eventually. i've tried different ways, chrome or nickle will look better longer. my durablue axle lasted a few years now it has dings an rust spots. my buddy bought a trx450r that had black tape on the axle.