I've got a small cast iron combination victorian fireplace (2ft x 3ft) being dipped. When I get it back, I want to 'burnish' or polish it to a grey/shiny finish rather than the normal black matt. I cannot find ANY videos or 'how to' guides on how to do this. So, does anyone know how to get the shiny/grey/burnished finish? Can any/every cast iron black matt fireplace be turned to a shiny grey colour or is there a special coating involved?