I usually train in cycles, I trained my SF as a C initially, for 2 seasons, then for the next 3 seasons I trained him as a PG, training 2 other PG's at the same time. Then I sold the other trainees, and trained my SF at C again for another season, now I'm training guards again for the last 2 seasons and have 2 great NT prospects alongside him at PG/SG (since I'm training scoring now).
It's been a rough ride, but at the age of 24 I can finally play him at SF and easily slide him over to PF/C when required. Hope to stop his training at 26... will be glad it's over.
Then have to find his heir...