The Retriever Trainer" by Freddy King builds extremely strong super confident hard charging straight as an arrow running 4-legged hunting/testing/trialing pups. It's all about following exactly the small steps in progression on the TRT website to have any pup with decent paperwork/lineage doing this kind of work at 10-12 weeks of age.
It does not get any more in-depth or simpler to follow than the "The Retriever Trainer"