Don't rush !!!!!!!!!
Sit, stay,Come and Heal are all you need for 9 months. Play with the socks by all means but don't rush or do to much dummy work.
If you do to much to soon you will end up with a dog that is not steady and will run in thinking every retrieve is his.
Until you can stop him when you want every time and he will sit and stay when you want him to then is the time to start using the dummy .
Remember the dog should have a good 10 years of work so a few months wait will be worth it.
Good luck and have FUN remember he's still only a pup.