Until your players individual training bonus and overall teaming bonus is max I do group trainings.
I use my 2 out of my 15 non storable boosters to get *2 training bonus.
And with the reaming 13, I give 1 each to every player after a match so that they are in better shape after the match.
For collective training use drills which don't have any GK attributes so that minimum condition is wasted.
After my training bonus is maxed out I train my Defenders, Mid Fielders, GK and Attackers separately.