You can dial it in by shooting a white or gray card and setting a custom WB setting for the particular setup.
Or you can buy a set of Warm Cards, which will help you "cheat" the WB that you want.
I've taken to using the presets most of the time anymore, I really like the Nikon WB presets, in some instances better than the Canon presets (especially under tungsten - the Nikon T preset cools the image more than the Canon preset). I have Kelvin adjustments too, but so far I haven't really needed to fiddle with them much.
Examples of some of what you've described (outdoor shots are the same model, and actually the same day, so that you can see the different effects on the same skin tone):
WB at Cloudy, flash set to stun with amber gel
WB at cloudy, no flash
WB at flash, flash set for fill, no gel
WB at flash, under strobes with no gels
And just because, this is WB at the tungsten preset, with who knows what for gels