What plan do Huck and Tom make for getting rid of the warts?

Tom and Huck plan to take a cat to the cemetery at midnight, wait for devils to come for the wicked man who died, throw the dead cat at the devils, and finish it all by saying a chant.

“Why, you take your cat and go and get in the grave-yard ’long about midnight when somebody that was wicked has been buried; and when it’s midnight a devil will come, or maybe two or three, but you can’t see ’em, you can only hear something like the wind, or maybe hear ’em talk; and when they’re taking that feller away, you heave your cat after ’em and say, ‘Devil follow corpse, cat follow devil, warts follow cat, I’m done with ye!’ That’ll fetch any wart.”