Q. How do you search for articles across multiple databases

Iceberg is fantastic in that it allows you search across most of our databases (most but not all) at one time.  The downside is that you loose some of the specialized search functions that some of the databases have.

I suggest that you search a couple of the individual databases first (you have more control) and then back yourself up by searching in Iceberg to see if you missed something (perhaps there was a database that you didn't think of using).