If you did change the speccoc for example and you adjust the main skins exposure buy -1.0 for example to make it darker then adjust the speccoc by -1.0 ,Well it depends on the color I want. If I would make it very dark red I would need to adjust the grey in the green channel to be darked for better reflection. But it's not that important you're right about that.
But you are right to open all 4 files adjust them all its still takes 5-10 minutes but its a nice skin ,
Also remember that it depends on the settings that people are using , I myself find that the Gamma @0.9 is best for my PC But some people may use 1.0 or even 1.1 , So in reality everyone is not going to get the true color of the skin no matter what changes you make unless you leave a comment saying best enjoyed at 0.9