Hi Steve,
I can simply tell you what I do, since I am happy with it, at least for natural lighting conditions.
RAW format:
With CHDK, I found that the DNG format makes life easier, since (among other things) the WB settings of the camera are contained in the DNG files. With DNG you can live very well without having a camera color profile. (Without DNG the RAW development software will use some default WB setting which can lead to color casted images.)
WB setting of the camera:
Since I found that it can be frustrating to correct bad automatic white balance in case of difficult lighting conditions, I generally set the white balance to "Cloudy" (even if there is direct sunlight or a sunset). Only exception: under incandescent lamp light I set the WB accordingly.
In most cases this gives very natural colors straightaway. Under direct sunlight the images can be a little yellow, but they are never far off from a good WB. Even under extreme lighting conditions, e.g. under leafy trees, the result are still pretty good.
Final WB adjustment:
With the above procedure, the remaining WB "misadjustment" is small and can be easily fixed with the "warm / cold" rsp. "red / blue" sliders of the RAW development software, e.g. in RAW therapee or Adobe Lightroom.
You mentioned "mixed light conditions": under certain conditions it can be impossible to find a suitable WB on principle, and that is if different areas of the image are illuminated by different kinds of light sources. In this case there is no WB setting which fits for the complete image.
Good luck!
electronicfreak