How make sure that this guy gets 36 mins and his reserve get 12 mins
If you find a opponent who forfeit his game it is easy(Starter A, Backup B, Reserve B), if you had an very easy scrimmage/league opponent you could try it with a good succes rate with this formation Starter A, backup A, Reserve B. Against an better or ok opponent, i would start A and make B backup but there B will mostly get only 7-10mins.
how make sure tis guy and tis guy get 24 mins each.
this is luck, but make sure that you activate "bench them" when they in Foultrouble, because you need to get the starter of the court.
And how make sure one guy plays 48 mins?
the easiest way and the most secure, lineup the player on all three spot and take only starters and backups to your lineup ... To avoid fould trouble i would choose "let them play" as foul action, else you will often get weird minutes on the training spot because of early fouls and "random" replacement at his spot.