Yes, if you care about the bonusses through power training. Otherwise just use hard and very hard drills. If you're just power training one player, you won't get the bonusses anyway.

The best way to power train might be to use the drills in which you have the highest level, since they will give the most progress (=less greens spent). But if those drills are mostly easy or very easy ones, it could take a long time to get your players to level up.