Ok, so it looks like if you want to train all 3 of them at once, it should be with inside training (rebounding, inside shot, shot blocking, inside defense). They all have fairly average ratings - nothing great, nothing terrible. So I would recommend rotating between 3-4 weeks of inside shot, 2-3 weeks of inside defense, 2-3 weeks of rebounding, and 1-2 weeks of shot blocking.
I also think since you only have 9 players you should buy at least one or two more cheap 18 or 19 year old big men (C or PF) from the transfer list. That way you can have 4 or 5 trainees at once. You should be seeing results in no time.
Also, I see you rarely played scrimmages last season. SCRIMMAGES ARE A MUST IF YOU WANT PROPERLY TRAINED PLAYERS. That goes for everyone. You NEED those extra minutes for your lesser players.
Good luck!
namssor