Training can definitely be effective in lower levels, even when your goal is a more modestly skill player rather than a killer U21/NT type. I trained a 19 yo allstar potential guy (Greg Lloyd) and got lucky with a 18 yo perennial allstar guy. There are other teams who have trained multiple star potential guys. So, it's definitely doable.
For all sorts of information about training, I'd recommend joining the USA offsite, where we have forums covering training all players. Then, you can send your training information to the crowdsourcing analysis, which gives hard details about the things that control training.
usa offsite forum is at http://s3.zetaboards.com/BuzzerBeater_USA_NT/index/
register there, then send a BB mail to sleet
(28628) or magiker
(30267) and tell then what email you used to register. Then they can activate your offsite forum account.
Information about the crowsourcing training analysis can be found here:
(203921.1)Also, you can use the training planner spreadsheet that rhyminsimon made, which incorporates data from the crowdsourcing project. You can predict how fast it will take to train players to certain skill levels. Link to training planner is here
(100218.2)]