"Cocker"...
The name of the breed comes as a shortening of "Woodcocker Spaniel." These dogs were originally bred specifically to be able to flush and retrieve the small woodcock from very heavy cover.
That said, I agree with the general idea of the previous posters, that many Cockers nowadays have the hunt bred out of them, and that you should try training the pooch extensively before trying to hunt over it. It's too late now to start for this hunting season. Mebbe the dog will work, next year, mebbe...
OTOH, my second hunting mentor (100 yrs ago, when I was a highschooler,) had a cocker he used for retrieving ducks, of all things. Well, it was the dog he had, and he was a duck hunter, and Mopper proved up to the job, so she went.
So, it CAN work. Good luck.