Having been in a similar role, I've found that the reality isn't that there are just dials you can tweak as the author says, but that time management is much more like what's described in http://www.paulgraham.com/makersschedule.html ... Once you take on direct reports, your day just gets interrupted more, and when it's interrupted more it's hard to do the same kind of deep thinking through problems. If you are new to managing, chances are you'll be managing people earlier in their careers as well. Since those new in their career need more guidance, you'll be interrupted a lot.
You can, of course, create blocks of time on your calendar. But as a manager, things come up: if someone on your team resigns or is having a performance issue you need to deal with, you can't just leave that for the next day.