My adult female cat came to me as a stray last year.  Soon after, she gave
birth to three healthy kittens that have grown into very healthy young cats.

The only lingering problem with the mother cat is her right ear.  I treated
her earmites for months, still do with Otomite Plus, however, I'm still
digging dark oily wax from her ears, several times a week and when I give
her ear a good rub afterwards, there is a wet, squishy sound deep in there,
near the eardrum even though I've done a pretty thorough cleaning.

She holds this ear kind of flat at times and when I'm cleaning it, she gets
her hind foot going, trying to claw at it herself so I have to hold her leg
to her body so she doesn't rip up her ear.

The vet only prescribed the Otomite Plus and had no other recommendation.

Is there any other medication that may work better?  How can I tell if its
an infection?

Thanks.
Jennifer