Built in messages

I think it will look too canned.  There are, however, a couple services on the internet that apparently will post on your forum for a fee.

I've never tried them, but I found an interesting article reviewing them:
http://www.websitepublisher.net/article/pay-for-posts/

Or you could ask a good friend to log on and chat with you on the forum.  That's what I did to get mine started.  At first it was just us, but them other people chimed in.  If all else fails, you could create multiple user accounts for yourself and talk to yourself.