Sometimes, even with a noise texture, if you just use a single one, it can still look CG, but if you take a second one with a different scale and maybe tweaking some of the other settings and/or offsetting position in some way, and then mixing the two together, it can look more natural.
As far as grunge color, you can always put it through a color ramp and crush the flags to get a sharper look if you’re using the result as a mask, though if you’re talking about the actual color of the grunge, typically, you want to avoid pure white and pure black to allow for more natural highlights and shadows (something I constantly have to remind myself about 😀 )
