I don't know my way of training session is convenient. I usually do 2 training sessions at the end of the day daily. Like, filling out the slots with 2 of attacking, 2 of defence, and 2 of physical. And selecting the whole team to train. I think its worth it. I rarely use the reserve players so i don't mind draining their health. But for 1st eleven i watch lot of ads to fill out their health before every match. And i rarely use the substitutes too, unless any injuries during the match. But i skip them with resources. So..my each training sessions cost average 15% of health.