You should hire a reputable bounty manager and let them organize the payment for you. They would be more than willing to listen to your requirements and they know the forum and its rules well. Not every type of giveaway can be posted and run on the forum and so you always bear the responsibility of what happens if you do run it and get banned by moderators - it could hurt the reputation of the project.

But paying the manger to do this, they would list it in the proper section. Bounties for altcoins or Services section for bitcoin. They would also take those accounts that are having a good twitteraudit score and thus you would be at ease.