When you have an inkling of understanding, you begin probing to validate your understanding. This is the start of the Orient phase. You may be wrong or right in your assessments - but you iterate from the small experiments. You hone in on what is actually true, which takes some iteration.
As for other Boydian ideas...here are a few:
Broadly applied synthesis: What made Boyd powerful was his deep intellectual curiosity. His broad understanding of history and thermodynamics made for a unique and insightful combination. He frequently quoted and made use of Heisenberg, Godel and other philosophers in his engineering work.
E-M diagrams: As a fighter pilot, I used his "Energy-Maneuverability" diagram literally every day. It's the foundation of all dogfighting across the world. And it was created from the computer time he stole from Wright Patterson AFB...and was then courtmarshaled because of it. E-M is closely tied to the OODA Loop, although the latter is far more broadly applicable.
Dont Forget Your Family: This was "anti-lesson" from Boyd. He immersed himself in his work. But it absolutely destroyed his family. He left them penniless because he refused to take any meaningful money from the government as a contractor in his post-military career. He was a Lion - but all men have their flaws.