SQL Server 2008 R2 service pack steps .....on cluster I have a sp3 to apply on SQL Server 2008 R2 on windows 2008 R2 cluster with four nodes and 6 instances. Node 4 do not have any resources but is possible owner for all the instances.

Steps I am planing 


remove node 4 as possible owner for all SQL related resources 
reboot node 4, apply sp3, reboot node 4
put back node 4 as possible owner for all node 1 SQL resources 
failover node 1 resources to node 4
repeat step 2 for node 1
repeat step 3 for node 1
failover node 4 resources back to node 1
put back node 4as possible owner for all node 2 SQL resources 
repeat step 4 for node 2
repeat steps 5,6,7 for node 2
repeat steps 4,5,6,7 for node 


Please verify and confirm or correct my steps. 

I guess sp3 + cumulative update for 6 instances per node around 1.5 hrs

Thanks in advance
I would make a slight modification to the procedure to reduce the number of failovers:


Remove Nodes 3 and 4 from the list of possible owners for each SQL Server Cluster Instance, leaving Nodes 1 and 2 as possible owners to preserve failover capability while doing the rolling upgrade.
Apply the Service Pack and latest Cumulative Update to nodes 3 and 4.  Reboot as necessary.
Make nodes 3 and 4 possible owners for all clustered instances.
Failover the clustered instances to either node 3 or 4.
Remove nodes 1 and 2 from the list of possible owners.
Apply the Service Pack and latest Cumulative Update to nodes 1 and 2.  Reboot as necessary.
Add nodes 1 and 2 back in as possible owners.
Leave the instances on node 3 or 4, or fail them back to node 1, if desired.


Microsoft has documentation providing more details if required.