It happens to Max. I trim that fur a little shorter. Ear cleaner works a bit but the best thing seems to be shampooing that area - making sure to plug his ear when I rinse. I use my finger to plug his ear but you could use cotton. I also make sure to add ear cleaner or ear powder to the ear after his bath to make sure the water is absorded and/or evaporated out of the canal.
it is important to keep the ears clean, they are like your nose and run~
Clean weekly using a baby wipe or special ear wipe, this should help.
Also shave the hair under the ear, from ear to ear going under the chin. This is called the Chin Strap or Throat Latch. This will help air flow and reduce heat and drainage.