Two days ago I changed my training method for bonuses like madflo19 suggested. Well, it seems to me that bonuses don't depend on drills' difficulties. They do however depend on amount of players in training session. Am I wrong here? I'm not sure, I need more tests.
If I'm right, there is no need to use any drills except Very Easy drills to get bonuses. Because if you're training your players in groups, it's obviously not that effective as training them individually.
Therefore (if I'm not mistaken), ideal training should contain only Warm-ups, Skill Drills and Video Analyses. I'm still trying to figure out the ideal recipe.
I currently have 20 players, and today I needed two sessions:

[2x Warm-up, 2x Skill Drill, 2x Video Analysis] (2 x 4.5% = 9% for the whole team)

and one session:

[2x Warm-up, 3x Skill Drill] (3.75%, without GKs, defenders and def-midfielders)

to get full daily bonuses. I find this method pretty good, but there's a room for improve, like probably train in two groups: (defenders + midfielders) and (midfielders + attackers) to save a little more energy. I'm gonna try it tomorrow.

To spend extra energy I train my guys individually with their own training schedules, so I can focus on skills each of them needs.

Any suggestions on that topic would be highly appreciated.