The term brute here isn't exactly the best one, batch would be more appropriate. To batch submit, you simply establish direct connection to the submission form using sockets or curl, and submit your post data headers which you construct from the batch via looping (assumed post). Ignore the HTML completely as its of no relevance.
Although if you have control, I would program it to handle the batch input via files and either upload them or simply open a specific file.
header('HTTP/1.1 420 Enhance Your Calm');