Hi Pixelzombie..... I was like you about the 'Highlight' setting and, since there was no mention of it's setting in Katrin's book, I left it at '0'.
I've never tried this using CMYK or on photos higher than a 300 resolution ... the 'after' picture below has had nothing done to it other than this healing brush method.... nothing to color, levels, etc...
I just tried this out for the peach fuzz removal and don't normally use this for skin but sometime might, especially if I made a larger grained brush to use with the smaller grained one..... I don't know..... could be OK....
Beth