Many signature campaigns already follow the logic of "CFNP" or "FULL" in the title, but that doesn't stop certain users from applying when it's full.
This is my approach when managing a campaign:
Rules:
11. If you don't follow the correct format to join this campaign, you'll be rejected. Think of this as a reading test 
Bad applications are a very easy way to reject users.
Having a standard means it has to be enforced
A standard also goes against the forum's mission:
the forum's mission to be as free as possible