Other posters have given good advice on technical aspects. I'd like to add my experience from moderating a large subreddit.

Focus on making it not fun to troll. Never acknowledge the disruption. Make all your countermeasures as silent as possible. Never address the script kiddy directly. Don't accidentally make a "leader board" or similar by counting number of bans/deleted posts etc.

Eventually it just becomes a waste of time to scream into nothingness and they will go elsewhere.