hi chedder i have vizslas and they get the crusty scabs on there ears i never see them scratching but I think that is the cause ,I saw the vet and he perscribed canural (spelling!!) although they didnt have dirty or sore ears the canural did nothing so I treated there ears for mites with thornit and the scabs cleared up (i left a two week gap between the canural and using the thornit) i now us one small pinch of thornit in each ear once a week and it keeps the crusty ears away! I also found the crustyness was relived by using olive oil on the crusty area once a week!
cheers kate :)