Well, it's not quite that random. More like veins of gold...you follow one until it stops, knowing that it may pick up somewhere else just a few feet away.
One tool that helps is a copy of the War Dept decimal guide -- it's a directory that assigned a number (and sub-numbers, sub-sub-numbers, etc.) to every conceiveable topic that might be a subject of interest to the Army, e.g., 'airplanes, general.' was 452.1. Each office filed its correspondence according to that scheme.
Here's what makes Sara Clark like mining for gold. What we call Sara Clark was created when Wright Field and its laboratories (there were about 12 during WWII) were told to 'clean out your files' after WWII. Sara's central files were boxed up, along with lab correspondence (which may be duplicated in multiple labs' files, but each w/different marginalia, maybe the photos, maybe not, etc.). This means that box x through box 34x might contain the files of the Propellor Lab, and box 35x through 42x might contain the files of the Instrument Lab, and so forth. But all of that went onto the same truck(s), and NARA numbered the boxes as they were taken off the truck(s)...and thus no longer in order, other than the files in each box being more or less as they had been in somebody's file drawer. Now, the only 'map' is the shipping documents that came with the boxes...they describe the contents, sometimes in exacting, folder-by-folder detail, sometimes just "papers." The shipping documents take up 105 sheets of microfiche. (By comparison, there are 250 boxes of shipping documents at St. Louis, but there was a sampling effort done in the late 90s).
So, what's needed is for someone to do a virtual reassembly of the filing cabinets at Wright Field...that's what the AEHS is attempting to do.