I'm confounded by the perceived allusiveness. I've never found it particularly challenging to invite a bro I'm hanging with to watch some porn together and rub one out, nor can I recall anyone ever passing. So is it a problem of not having friends? Or just not knowing how to broach the subject?
If the latter... and if you're really hung up on doing this.... next time you got a bud over hanging out (or a roommate?), put on the movie The Divide. It's a total guy, end-of-the-world, psychological flick. You might drop into the conversation before hand some comment like, "Fuuuck. I've got the worst blue balls today. I haven't nutted in like 48 hrs." You know... just tee that shit up. Then, about 3/4 through The Divide (spoiler alert), there's this fucking awesome sex scene. Real porn style shit. When that ish comes on, just make a big deal of it. "Shiiit. This just got hot." Pull on your dick through your shorts while you do it.
Then, when your ready (don't even have to wait for the movie to end if you don't want), just say "Fuck dude. I really need to rub one out. Mind if I put on some real porn?"
Another spoiler: he won't say no.
Then from there, just be super casual and cool about the whole thing. Assume he's going to jack off with you. Throw a box of tissues on the coffee table. Ask him if he likes lube with his porn. Be jokey about it. Grab him another beer. Then, after you've put on some skin flicks, you just start playing with your dick through your shorts a little bit... eventually, just pulling that cock out and slowly stroking it.
It's no rocket science and it's not taboo. Just be the person you want to be, do the things you want to do, and the universe will reward you. You might be surprised too after initiating a mutual jo once just how quickly your friend becomes the initiator after that.