@ajax - I agree with @afre and @ggbutcher - simpler is better. When white-balancing a raw file, as @afre noted temp/tint is an abstraction from the actual white balance multipliers. Agreeing with @ggbutcher, for just plain white balancing a raw file I’d just as soon not even see the temp/tint sliders. Even the various raw processors all have different temp/tints for nominally “the same” white balance (for example “daylight”), but the actual white-balanced image produced by each raw processor is very similar.
If the image isn’t a raw file, then find a nominally gray spot in the image and in GIMP use Levels to white balance, just make sure you set Levels to work on linear RGB and that the image is at floating point precision. You’ll probably need to move the lower Value slider to restore proper exposure - it’s easier to do this sort of white balancing in RawTherapee, darktable, etc than in GIMP.
On the other hand and depending on your goals, RawTherapee’s CIECAM02 module is considerably more than just an abstraction from raw multipliers. But again, there’s a learning curve, that’s well worth climbing depending on the goal, for example preserving or restoring the “color of the light” instead of white-balancing it away. But this would be digital image processing 201 or higher maybe not so useful for most editing tasks.