Yes, diluted Hibiscrub works a treat.
We make up a 10% solution about 2 inches deep in a plastic jug and, with the cocker either sitting or standing, lift it up under each ear until the bottom of the ear is in the solution.
If you use a large enough jug you'll be able to get one hand in to gently massage the ear while in the solution. No need to rinse it off afterwards, simply dry the ears.
The same dilution is ideal for keeping scratches, scrapes and small wounds clean as well and we find it useful for dipping paws into after they get muddy.
Hibiscrub can be obtained from most chemists or online from Amazon where it's about £6 for 500ml.
Bob.