Archives are amazing places. Did you get a chance to look through finding guides? Finding guides are usually the crucial element in research: the catalogs and databases are typically large and not very detailed, so they can tell you what the various collections and sub-collections are, and they'll tell you that a bunch of things exist, but not much more than that. Finding guides are usually one level of detail greater than that. They'll look at a single collection and give more detailed descriptions of just what each item is. So, if you're looking at really big collections, a finding guide is your best friend.