@Aaarrrgh
About scenes.
You can create 2 types of scenes: RP or Non-RP.
Non-RP scenes work the same as periods or events. RP scenes are more complicate though.
If you choose to create a scene, you are nominated the scene GM, but everyone can participate. The GM makes a question. Answering that question is the purpose of the scene. Then the GM chooses the characters that must participate and the ones that are banned.
Every player chooses a character. You can choose to create your own character, but all characters named by the GM must be picked first.
You can control more than one character, but you cannot control other named characters. For example, you want to slap someone. You don't slap it. You move to slap it. And that player decides if he will take the slap or not.
I believe that covers almost all of it. In addition in RP scenes, people don't need to go in order. It is like a mini-game, inside a bigger game. If you have any other question, just ask.
Personally I think it is kind of strange to create a RP scene without building at least some of the characters first, but that is your choice. As long as you are able to create the characters and the scene purpose, it can work.