You have several methods that enable you to obtain followers and some of them enable you to buy them, but if you want real followers from the forum, you have one of two options:

 - Assign a campaign manager: You can hire a manager to promote your channel and then pay to him.
 - Payment to users: You can pay to join your channel after you put the money in the escrow and then give about some satoshis to each user who made a certain contribution.