I am sure there are many ways, however I would:
1. Click on the grey card, set your WB in image one.
2. In the upper right corner of the screen hit the right slanted up arrow to copy the image selections.
3. Select all the remaining images you want to apply set WB to, this is done with different key strokes mac and win
4. Once all the images you need are selected, in the upper right corner of the screen hit the leftward down arrow, this will apply the copied image selections to all the reaming images.
It takes less time to do it in C1 than it took me to write this.
Paul Caldwell