I have also never had to try this either so I would have to agree with Perry that thats the only safe, guaranteed way to do it.

also the fact that I could find nothing on this would suggest you have to do it that way.

Having to apply an SP and a CU (and maybe a security patch as well) cannot be that unusual so you would have thought some guru or microsoft would describe the process for a cluster, but they just stick to how to apply a single upgrade.

You could experiment for us but I wouldn't recommend it except on a sandpit server! 🙂