Followers are people in your WNW orbit with varying degrees of acquaintance, from colleague to co-working space neighbor. Vouching, on the other hand, is a level above this. When you vouch for someone you are saying that if you were unavailable any vouch would be a good replacement. Therefore, in order to vouch for a Creative you both have to be Following one another. To Vouch for someone just click the "Vouch" button below their Followers. That person will be notified by email that you gave them your seal of approval.
Here is a video demonstrating how to Vouch