I would strongly suspect different metals are used for different finishes - but I know that IoWSG sprays a lustre finish on using Stannous Chloride. (Tin)
This isn't an overly mirror-like shiny surface as some are, but somewhat matt.
I've got a "Balloon" vase, which has a layer of stannous chloride sprayed inbetween casings - it gives a subtle, slightly glittery, rainbowy effect inside.
In Wedgwood Fairyland lustre, the lustre can be a gold or green shade, Carltonware used a goldy red (on Rouge Royale), Zsolnay use an eosin glaze with a gold coloured lustre.....