To get full training a player must play for 48 minutes in the position(s) that you are training. If he plays less than this he still gets training but it is not as effective. If he plays more than 48 minutes it is still exactly the same as if he played 48minutes.
The fastest way and most effective training is 1 position training. This is when you only train 1 position either PG, C or SG (Jump Range is the only option for SG thou) By doing this you can train 3 players a week by playing each of the for 48 minutes in each of your games. There are a few types of trainings that do not allow 1 position training (Jump Shot, One on One and so on) so for these you must use 2 position training, which is just about as effective as 1 position training (only for the ones without 1 position training)
Young players train faster than old players so the most effective way to train is to have 3 young players (18-20 year olds) who are either all PG's and SG's or PF's and C's and do 1 position training having 1 of them playing the full game at PG or C. Then if a player doesn't play the full 48mins (fouls out or gets injured) play him at SG or PF in the next game and do 2 position trainng for that week.
This ofcause is all just my opinion based on what I have read and what seems to work best from my experience (and from hearing about some results from friends trying different training tactics) but if I were you I'd look through some forums and read as much as you can.