For some reason, to set a custom white balance in an IR-Converted Nikon D70, one must first change the exposure compensation to -2.0. After that, then under direct sunlight, photograph something that should be "white" in infrared (foliage, etc.).
I actually use different colored cards (e.g., green, red, blue) and fill the viewfinder with the card under sunlight and out of focus to obtain a custom white balance.
Experimentation is THE key to obtaining personally satisfying results in IR: experimentation in camera settings; experimentation in post processing steps. I have found little help in trying to duplicate another photog's approach in IR photography; there are just too many variables -- even when using the same model camera and the same strength IR filter.
Good luck. Post your progress for all to enjoy.
