I would also go with the above as i have polished many metals. If you were to lacquer it and the lacquer broke down later it would look terrible.
Solvo Autosol will bring the alloy up to like a soft chrome, once there the occasional clean with more solvo and a soft cloth will keep it like that. On the initial polish make the cloth go black then clean off with a soft cloth.
With brass solvo can also be used but then finish with Brasso. Both will be a very dirty process lol.