Ear infection every time after grooming

I have taken my dogs to Sloppy Kisses twice for grooming. The grooming is very nice, but twice they had ear infection within 48 hours. I had taken it up with Janine, and she was most sympathetic, but totally uninvolved, and suggested I (again), get something from the vet (at my cost). Her groomer apparently does plug the ears with cotton wool, but gets it wet, so there is no point. She promised that she would get it right next time, but I do not think that there should be a third (next) time with expensive ear infection.