I wash my cockers ears fairly regular in a plastic jug with warm water and dog shampoo, if your dog will let you try and dry a bit with a hairdryer...but that can be tricky as its so close to there face.
Doing often maybe every 10 days or so keeps their ears free from crusty bottoms
you will have to keep them a gentle massage to loosen the harder bits but hopefully it will go after a couple of washes. I do brush my cockers ears every day too which helps...these cocker are high maintainance