Thanks! Should I need to do this for each of the shading domains, or can it be done once?
Yes. Each of the domains that are to change must be set up as Head Wax (bless his heart for the great, and concise explanation) - but anything that doesn’t need to change can be left alone.
However, you will save yourself lots of time by doing the following:
Set up the first appearance. Example, your base M4 texture.
Go to ‘Edit > Remove Unused Masters > Consolidate Duplicate Shaders
Now, in the texture room, you’ll notice that you’ll only have three or so master shaders to change for the skin appearances. Just change those and you’ll be good to go.
YouTube vid I did for Genesis using the exact same method: