I haven't used an air popper since the late 70's/early 80's, but the kind we had at home needed to have the area where the kernels went brushed out, because otherwise old kernals would just roll around in the hot air until they burned up.

The sugar in kettle corn would certainly mean more cleaning, but I don't know how you can get away without cleaning out a sugar and oil combination.

By the way, if you ever get to Salem Willows in the summertime, there's a popcorn stand that makes unbelievable kettle corn and *warm* caramel corn that's to die for!