The fine finishing polish is a wax base. next would be wax, as for shellac I will not use that stuff on anything, That stuff is evil, thats just me.
as time goes on, it will tarnish some, but you will also be putting more oil on the machine so rub the excess oil on to the steel. I have machines that where polished 20 yrs ago, they still have a nice bright look, but not the mirror finish they did have. These face plates , handwheel never were bright like chorme
anyway this isn't any different than polishing silverware or pots and pans, jewelry