I know it is not ideal, but could you get another collar for the underground fence, and give it to the neighbour? Surely a gift would make him happy?
When you put the oil down the ears, it helps to squidge it about. Then take a nice clean bit of kitchen towel wrapped around your finger, and gently have a good ol' clean out in the ear canal. I used to have a basset hound and had to do it every week as a preventative measure. They actually quite enjoy it - Mom is scratching THAT bit
Good luck !!!
