Best way to update sysNAND with A9LH?

I've seen people with a9lh say that they have updated their sysNAND to 10.6 with a9lh installed. How is this done safely? Will updating through the System Settings remove a9lh? Should I use sysUpdater? Do I need to remove a title from the update pack so that it doesn't remove a9lh?

Thanks!