If I might pop in here for a second? I've always just operated under a self imposed "wait two posts before posting again" rule. The only times I would typically fail to post again after the aforementioned two posts would be either because A: I engaging in dialogue or actions with one specific person where others could not respond, B: I had no idea what to post, or C: I was busy. In the case of the last two I would usually make mention of the issues at hand. I find that waiting for 'X' amount of posts to go by before a person posts again rather than having a turn order is one of the easier ways of getting things to remain smooth. The tricky part is to make sure everyone is properly tagged in a post and/or ensure that two people interacting are not doing so in a manner that would be considered important for plot reasons/ severely interfere with things chronologically. The tagging posts bit is fairly simple, just clicking the mention/quote button will do, though the chronological issue might be a bit more difficult. In the end I find that the best way to solve that issue is by having interactions that have been frozen in place for a bit be mentioned and treated as though they occurred in past tense before having the characters transition over to what ever may be happening currently.