Grid 11gr2 - Multiple Listeners under a SCAN Listener

I have a 2 node RAC cluster setup running under Oracle Grid Infrastructure 11.2. I have 3 databases on the cluster. I have a SCAN Listener setup and working properly I believe, and it resolves down to a single Listener for all three databases. Ultimately, we want all three databases running on spearate ports (so we can restrict access by vlan to those databases). I have seen that I need to open both ports in order for sqlnet access to be succesful (the scan port and the local listener port).

Based on that I believe I want to create 3 new local listeners - one on each port - and then change the LOCAL_LISTENER value on each database to the appropriate new listener. I have not been able to find any documentation on the proper steps to changing the local_listener parameter under RAC. Is it a simple alter system or is there more that needs to be done for the change to register properly? Also, do I want to create the local listener under the Grid home or the database home?