Angel lore from outside sources for use in the story.

“Angels transcend every religion, every philosophy, every creed.
In fact angels have no religion as we know it …
their existence precedes every religious system
that has ever existed on earth.”

St. Thomas Aquinas

Angel Lore at Supernatural fan wiki

Kripke’s angels seem to be influenced mostly by biblical sources (no surprise there) and other movies (also no surprise), particularly the military structure.

Angels in both Dogma and the Wim Wenders movies wore physical armor, though with WW angels it was not visible unless they took it off to fall. Wim Wenders angels wore overcoats/raincoats and spent a lot of time just watching; Castiel’s expression of empathy, the hand on the shoulder, also reminds me of WW angels and the way they embraced mortals to comfort them. Dogma angels wore jeans, though it appears the original plan was red robes.

Dean probably got the idea that angels are “junkless” from Dogma, as well. (Whether SPN angels are or not is open for debate: for example, since Castiel is in a vessel, is he neutered? That would be a bit extreme, particularly if the vessel is going to get un-possessed at any point.) However, Dogma angels had their own physical forms and did not need to borrow a vessel, while Kripke angels need to. So . . . I’m thinking the junkless thing is just an assumption on Dean’s part.

Movie angels tend to fall into three categories:
*warriors
*messengers
*guardians

Movies:
Wings of Desire
Dogma