>>1
First, you should examine the html source to figure out the form fields. Either that or use Firefox + LiveHTTPHeaders addon to find out what a thread reply post looks like, after doing a test one.
Then, carefully read the documentation for curl and figure out how to construct your HTTP request with its available parameters. To spam, you should run this command repeatedly, until you are banned for being a dick.
Finally, don't bother us with this useless shit ever again.