Signature is implied in Bounty campaigns and Airdrops are most likely have in common with the Bounty campaigns too. You are only talking about promotion of ICO in Social Media Sites, BCT Forum, and content creation, which is indeed the most easiest way to promote your project. Yet, if you really want to have a successful project, you must also do your best to talk to your investors and talk to any companies who wants to have a partnership with. Hence, their company might help you promote your ICO project.