1. You simply make a second account.
  2. Make a post on any board of your choice with your main account.
  3. Then spam comments from your main account on this post. 4. Logon to your alternate account and vote all these comments.
  4. Login to your main account again and delete all these comments.
  5. Repeat steps 3-5.
I automated this with some post requests and it could be scaled up much larger in a shorter time frame. If you need any more info, I can provide more.