White balance setting is different between cameras. If you're taking a shot to use for white balance setting, aperture priority is an easy one to use. Try to fill the view with the white card, your hand won't do the job.
Another way, if it's only a few shots you want, would be to have a white card in the shots somewhere so you can use software to balance the colours when you get home. If it's at the edge of the frame you can crop it out later.