Hi hi hi
Do you remember the Cas trying to masturbate secretly but in public post? Would love to know where exactly he learned that cuz I'd bet he stumbled upon Dean's porn stash or something lol, that also gives me more ideas like what kind of freaky things he'd learn from his porn 🥸 Have a feeling Dean would be into crazy hentai stuff (which he totally doesn't imagine Cas in)
So,
In my head, yeah, is from porn that Cas learns to masturbate
(Why the hell my corrector keeps suggesting me "masturabate"??)
But I don't pictured it as him stumbling on Dean's stuff (although that is very good too!)
In the scenario that I thought, Cas has the initiative of searching for adult content as a form of expanding his intimate knowledge with his own body
So he learned a lot of things about his form, the things he likes and doesn't like, and, of course, he also learned how to identify if his body is healthy
But he likes the gooning part a little too much
What wouldn't be a problem if he got most of social cues, but... is Cas, so, yeah
I'd also say that Cas taste in porn would start on solo videos, most by people that have a similar body like his, then he would adventure here and there on channels of blonde guys with green eyes and stuff (consciously and guiltily), then he would could get into more "unusual animated stuff", specifically the unrealistic ones like tentacles ((I have some art of it by the way ;D) shout out to our guy Dean) and fantasy like size difference
But the priority is solo porn
Again, this is specific for what I thought about Cas shamelessly masturbating like at noon in the kitchen
Hope that was satisfactory!
(Also, you have that feeling because Dean IS into that kind of stuff, you can bet on it)