If you mean like, traditional RPing threads… Generally what B and I do is wait until the characters kind of figure that out themselves by blogging (For example, sending an ask or whatever about “Hey, wanna go [insert a thing here]?” — “Sure, I’ll pick you up!”) and then talk to the other mod about if they want to do a thread, someone makes the starting post, etc, and we go from there and continue to RP pretty traditionally.
I personally tag those with a certain tag so my blog is organized and so my followers know it’s not my character blogging like he normally does. B has picked up this tagging habit up as well and I’d highly suggest it, especially for the organizational benefits. It’s also super useful for your followers if you write shorter posts, because sometimes people might mistake it for an open thread/an online blogging thread and jump in accordingly. Thankfully we haven’t personally had a whole ton of issues with this, but hey, better safe (and meticulously organized) than sorry.
If you mean just the character making text posts and starting online conversational threads, think about what you’d personally blog about. Your day, a movie you just saw, some dumb stuff you saw on your dash, etc. Just have the character comment on whatever strikes fancy and roll from there! Usually someone will comment on it and get something going. If you see someone else making posts like that, go ahead and have your character comment on those, too.
I hope that answered your question? Lemme know if not!