what klunk said .. using a clearcoat / thin film material if you have shader support for it
if you don't have shader support for clearcoat it's harder - you can't use the normal map cos it'll make the surface look lumpy and you can't mess with roughness cos you'll lose the overall sheen.
The simplest option would probably be to max() the black and white noise with your specular(and metallic) - that should give you sparkly bits where you see highlights but it won't really look right since areas outside highlights should also sparkle.
To go any further you'd need to start doing lighting calculations against the normal map and feeding the result into emissive - that will probably be a bit limited (eg. you might only be able to have it react to one light)
I would also add a grayscale channel and UV * something to shift and mess UV for flakes a bit because with such scale they will look repetitive as hell . While in smaller scale they would just disappear in mip levels.
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something like
both alpha for the normals and diffuse and a mask for the specular/metal/reflection effects
and for the normals
and go from there as the rest is just clear tinted plastic
if you don't have shader support for clearcoat it's harder - you can't use the normal map cos it'll make the surface look lumpy and you can't mess with roughness cos you'll lose the overall sheen.
The simplest option would probably be to max() the black and white noise with your specular(and metallic) - that should give you sparkly bits where you see highlights but it won't really look right since areas outside highlights should also sparkle.
To go any further you'd need to start doing lighting calculations against the normal map and feeding the result into emissive - that will probably be a bit limited (eg. you might only be able to have it react to one light)