I see drilling as really perfecting a technique or question type that you can then apply on a PT. Drilling is like a fighter practicing a certain move and PTs are like a sparring match, they both serve a different purpose. Drilling for me is helpful to really key in on issues I'm having, such as with a certain type of problem like LR Weakening or RC Science. You can do different types of drills, such as speed drills, to really nail down things like timing and what to look for specifically. If you find yourself hitting a score plateau while taking PTs, like I did, try looking up some different types of drills you can do and try to complete them in the target time.