Have you 3D coat ? if yes the process is quiet easier
I sculpt in Zbrush but I backed and refine the maps in 3D coat
3D coat read whole UV Groups and export them agian without such a crumbersome workflow needed . Import the the Highpolymesh in the retoproom , then import the Low poly mesh and covered over the High poly and bake all needed maps at once .
export the maps done ...
also easier, how to see the example with the eyebrows you can re position or paint the eyebrowns directly on the model .
In this example with photoshop is like more try and error without see what happend