Near the bottom they mention using more than one wheat stream to achieve something like deniable encryption. If they ask you for the key, give them the one that produces innocent-looking messages.
Depends, how good are you at creative writing? I can think of a lot of messages you might send to someone that you'd want to be private that aren't nefarious plots. Weird fan fiction. Deviant porn. Messages exchanged with a secret mistress. Depending on the situation, you might even want to give them a fake copy of your nefarious plot. Include more than one extra set of messages if you like and give them whatever keys you like in whatever order is appropriate.
How easy is it to produce a stream of messages that is fake but looks real?