
My little Patterdale had Parvo when she was 6 weeks old, but being a tough little cookie she survived but she was so run down she then had demodex. We used the washes 3 times a week, diluting the alludex in a washing up bowl stood in the bath. She was small enough to put into the the bowl. I suppose it took about 6 weeks to clear her of the mites, but we gave another 2 weeks on top to make sure we got all of the little blighters. She has been clear ever since and she is now coming up to 8 years.
It is awful stuff to use and you must be very careful around the eyes, but it works and is well worth the effort.
The demodex burrow right down into the body, they are not a surface mite, so it takes a while to reach them all, for this reason sometimes a scrape will not pick up and show any mites, but it does not mean they are not there. For this reason you tend to go on an extra bit more just to make sure.
Good luck.
BTW years ago I had GSD with the demodex and she had to be completely shaved as the aludex could not get through her thick coat, she looked like an over ready turkey. At least my Patt did not have to go through that indignity.