IDK, man. It's not that hard to just check a few of the communities and see which ones are active, and then post to those ones. And the benefit you get, for asking people to take literally a couple of minutes of effort to sort out how to get involved with some particular topic, is pretty significant.
I'm not trying to say not to make good solutions to it, but also, trying to make everything maximally easy carries a significant down side, in that it attracts people who want to put minimal effort into everything (including their posts and their interactions with others once they've arrived on the network.)