I think you should have a slack bounty cause that's the best to communicate in the bounty campaigns to communicate if there is any problems that may occur in the campaigns. Also it is very easy to use and the participants and the developer can respond efficiently and effectively .Thanks you.
slack platform is a bad choice lately due to the fact that more fake groups are spreading on it and this could lead to some seriuos problems like scamming and hacking , that is why slack nowadays is not really recomended to be used as a comunication tool instead bounty campaigns are only sticking in telegram channels.
The bitcointalk campaign is a great solution for you to follow from organizers such as social media, signature campaign, blogs / articles, videos, etc. The organizers also provide some requirements that must be met by the participants, for example a lot of friendship or followers, the number of characters, etc.
Speaking of this, he should also consider to pick up a trusted and profesional manager like yahoo. in order to operate and manage his bounty or signature camapaigns because choosing a campaign manager randonly is a bad choice to the fact that it can lead to spamming and unhealthy performance of its participants.