Our working cocker pup came home in August. It was tough going but he's currently in a delightful stage at almost 6 months (until adolescence kicks in!).
I wrote about this on another thread recently but I was naive about how long toilet training would take. I did a tonne of research but barely came across any people talking about the pups taking longer than a couple of weeks. Lots of 'my dog is so clever and was fully clean in 3 days.' We did everything right and it was a slog, but it eventually clicked with him at around 4.5-5 months and now he's great. I was so stressed at one point that he would never understand to pee outside! So just to make you aware that it may take a lot longer than you expect. Every dog is different.
Also agree with @EdithStourton re working them in some sense. This is so important and is the difference between a happy dog and a frustrated destructive dog. There's so many poor WCS who are relinquished because their needs can't be met. We are going to start gundog classes next year, so we can gain the skills to keep him happy and his brain stimulated. We have just completed a basic puppy skills class with a gundog trainer, and even though it wasn't gundog specific as it was for pups, she did talk a lot about harnessing that natural ability and working with them. I'd recommend trying to find a trainer like this who fully understands the breed.
There was a lot of skills I had already taught him by the time he started the classes, such as sit/stay, recall to whistle, leave/drop, basic retrieves but the course taught me how to do things in a slightly different way to suit my dog. She also taught us how to teach him to settle which has been brilliant as he's now so chilled in the house.
Agree with pp who said about getting them off lead as early as possible. I was terrified about it but had him off in the woods from the first day we could walk him and it's paid off massively now. He is brilliant and stays close and its a joy to see him dashing around doing what spaniels do,
Your pup will be super clever, trainable and eager to please. Mine definitely is a classic spaniel Velcro dog and loves to be attached to me at all times!