You can’t use RT to set the white balance and then somehow squeeze out the RGBG multipliers. Most raw processors provide several ways to set the image white balance, including setting the RGB multipliers. RT does not. I don’t know why, but maybe this is tied up with how RT pre-white-balances or something.
Across the various raw processors, the “meaning” of RGB multipliers is more or less constant, meaning setting the same RGB multipliers in darktable, ufraw, dcraw, photoflow, photivo produces pretty much the same final image colors. But as RT doesn’t provide access, you can’t share the same multipliers when comparing output from RT and other raw processors. The best you can do is hope that the presets and “camera” are the same for the raw processors you want to compare.
Unfortunately, the temperature/tint slider values for the various raw processors don’t correlate at all. The “same” temp/tint taken from one raw processor and fed to another will produce more or less different colors.
This page has summary information for various raw processors’s options for setting white balance. PhotoFlow wasn’t released yet when I put together the information: Raw Processor Review, Part 1
When using dcraw, I find it convenient to get the white balance multipliers from UFRaw and then copy them over to dcraw using the “-r” multipliers. Open UFRaw, set the white balance you want, then click on “Options” and select the Configuration tab - the white balance multipliers are available under “”.
The exif data in the jpeg comes from the raw file, and shows the white balance for various shooting conditions such as daylight, cloudy, etc, as given by the camera manufacturer. Use exiftool at the command line to examine the full contents of the raw file and the corresponding jpeg: “exiftool filename.ext”