He's interviewed in Eugene Jarecki's Why We Fight and Jason Vest tells us,
For most of his 26-year career as an analyst in the Tactical Air Division of the Pentagon's Office of Program Analysis and Evaluation, Spinney was a formidable force in the service of anyone seeking to decipher the complexities of Defense arcana. Indeed, says Jarecki, "I think anybody who's decided to make a study of the inner workings of the Pentagon hasn't done his homework if he hasn't talked to Chuck - so many roads lead to him, which is why I knew it was essential to have him in the film."It's in that cube as I remember him. Auditors have time to kill between jobs and we'd wander and take a look at him out of curiosity. I can't remember him saying anything of consequence other than I was sympathetic to his low-tech warfare views (all badly wrong in hindsight now).
First, however, Jarecki had to track down the analyst - no small task. There was a time when it wouldn't have been a challenge. After Spinney landed on the cover of Time magazine in 1983 - for congressional testimony in which he critically parsed the systematic problems and excesses of the Defense budget - a wrathful Caspar Weinberger, then Defense secretary, wanted Spinney fired. Though a bipartisan crew of congressmen (including then-Rep. Dick Cheney) successfully stayed Weinberger's hand, he attempted to mete out a punishment of sorts by not only freezing Spinney at the GS-15 level, but even going so far as to order a plaster cubicle built around him (colloquially known as the "Spinney Wall"), lest his fiscally conservative influence corrupt younger, more impressionable analysts in earshot.
I don't know why he was hard to find as you find him writing in Counter Punch and he has a website.