we have home trained our gemma to come with us beating. we got her at 10 months of age and started straight away. One book we found helpful was "training the working spaniel" by janet menzies. we also attended game shows,country fairs etc. anywhere there would be working dogs , to pick the brains of trainers and owners. it is surprising how much free help and advice you get if you show willinness and genuine interest. Gemma now 20 months old is with us on the beating line, flushing birds with the best of them, and knowing that she will only get better fills us with pride. She will retrive small game, a pheasant is a bit big for her as she a tiny cocker but she will get round that.
On saying all that, when we get our next pup (from new) our plan of action would be basic training then start adding the "extras" at about 6 months. but it depends on the dog. like people some are better learners than others. we have been spoilt by gemma, she was born working, cannot switch her off.
Good beating, believe me it is so much more fun with a dog, especially when it is your own