Ear hygiene is very important with cockers so it's best to start when they're young
Take it nice and gentle and he'll soon start to look forward to having his ears scratched while you're checking them out.
Our two get their ears checked and sniffed daily
and, while a slightly warm waxy smell is perfectly ok, any disagreeable smells should be investigated.
Try to keep the hair at the entrance to the ear short by gentle clipping with a scissors. This allows any excess wax to escape naturally and helps to prevent grass seeds and other foreign objects lodging close the the ear canal.
While there are commercial products available to assist with cleaning the ears, a small cotton swab dipped in warm water is perfectly suitable for cleaning a puppy's ears.
Ear problems can be very distressing to cockers and also quite expensive to cure once developed so a check of their ears daily and especially after walks can make life so much easier for you both.
Bob.