Throughout entire Force Awakens, Finn has no idea what he's doing. He doesn't know Millenium Falcon has 2 guns, he's a terrible fighter, and he is always trying to run away. In addition he is a sanitation worker which implies he is private-level (to speak US military out-of-universe).
Does Finn have any strengths, either in movie, in canon, or out-of-canon?
EDIT: I am writing a fan fic, otherwise I wouldn't need to know this.