Several blogs tell you to add shared disk to your Windows Failover Cluster nodes one at a time. If your disks reside on Netapp storage you can speed this up by adding disks to both nodes at the same time.
Just make sure you have created your cluster before adding disk. Then use SnapDrive to Create a new disk or Connect to an existing disk. You will now be able to create LUN mappings for both cluster nodes at the same time.