I was playing my first battle with a Cauldron of Blood the other day, and used the blessing Fury of Khaine (+1 attack) on my Cold One Knights. At the time it seemed obvious to me that this applied to both rider and unit, but I have since second guessed myself. I lost the battle anyway, so no hard feelings if I got it wrong, but I don't want to be cheating by accident. The FAQ isn't very helpful, and while there is probably a universal rule somewhere in the main rulebook, I haven't found it.