As any Devon owners will know, they are a greasy breed, being a bit lacking in the hair department, so it all seems to collect in the ears. Vet ALWAYS checks him for earmites (that I am charged for), even though I explain about the breed having brown, greasy stuff in their ears.
The breeder recommended I use water based baby wipes, and his ears needed doing weekly. I since found some cat wipes called "refresh'r", and only have to clean his flappy ears about once a month.
Just thought this might be helpful to any other Cornish, Devon or Sphinx type breeds.