I think you're mistaken. Signature is usually part of a bounty campaign. The average bounty campaign is usually split into the following: Signature campaign, article writing, youtube videos, twitter retweets & likes, Medium claps, etc. A fixed percentage would be offered to each campaign, and users would receive stakes, and the total tokens allocated for bounty would then be distributed accordingly.

For an airdrop campaign, you could launch it after the bounty campaign, to attract new investors.