If I were an actor then I would go anonymously go to various on-line boards / discussion groups and plug my stuff. Self-promotion can be very helpful.
I'm skeptical, this kind of undercover promotion is rarely subtle on a forum. If the user don't use a too promotional tone, he will be betrayed by his redundant interventions and be fastly tagged as a fan-club president or a manager. I saw that on some occasions with music board.