I would enable the troll mod on them. It's fun watching the posts they are creating, but with the troll mod means you can see the posts, but the forums members won't be affected by it. If you ban them, the troll will just come back again, using different IP's, rejoining.
I ban them too; but I will usually warn them first. I hear it's a good idea to make a board on your forum that tricks bad members into thinking they are not banned, when they actually are. So they could cause terror on one board and not be able to see any of the actual boards.
Sometimes though, saying random things that make no sense can scare trolls and jerks away.
Tell them you went to space with a hippo, they'll think you're insane and leave.
I don't ban them, I put them in new usergroup and redirect all the members in the group to either meatspin.com or Lemonparty.com.
So, I'm the one doing the trolling really... like a boss.
There are two(?) types of trolls. One group which are legitimate trolls who annoy users and whatnot. Then there's a group which makes others laugh for comical effect.
If you isolate a post without context, the two may seem alike. However, context is very important. It might be a thread where comical effect is necessary, so you would be in the wrong to ban someone of the second type. However, if they are going onto random threads and literally annoying people, even making rude comments, then it should warrant a ban.
CloudFlare blocks almost all spam accounts before they even get to the site, though when they do get through, I normally let my moderators handle them. Good practice for the end of days =]