all in all, it is a really excrutiating process and the training system is not very friendly for sf training at all imo. PG then Center then PG then center..over and over and over again.
Definitely a long process but you shouldn't see your trainee as your star guy until he's ready. Buy good old vet (or 2) and play him in league games and give training to your SF in scrimmages. That way you won't play your SF out of position in important league games and your performance shouldn't suffer. Meanwhile, your trainee will become better and eventually he'll surpass current starters.
Also, by changing training week after week, all of your players will receive training - not just outside guys or inside guys.