After a morning taking a White Balance reference shot every half hour there appears to be little difference between the manualy adjusted PP "custom" balance from the reference shot and the "As shot" WB.
For what shooting scenario? If I'm outdoors, I find AWB effective enough 95% of the time. If I'm having white balance issues indoors, I dial in a custom value using live view until what I see in the viewfinder equals what I see with my eye. The goal is to get is close enough, then tweak the raw image in PP if necesary.