|No getting around it, this sucks. But...|
The book uses a four-limb staff without instrument assignments, but I default to a normal timekeeping position with the right hand on a cymbal, left hand on the snare— and feet on the normal hihat and bass drum, of course. Lately I've been doing something different: playing the cymbals on all notes in unison with the bass drum, and playing the snare/toms on all notes in unison with the hihat— the left foot. This causes you to do a lot of moving around, with both hands moving between the cymbals and drums.
Usually I try to make things as easy as possible, but this actually makes the exercises more difficult and time consuming. And it requires extra focus— since both hands play both drums and cymbals, you can't rely on your ears to tell you whether you're playing the correct hand for the pattern. But this is a more realistic way of playing, so the patterns sound less arbitrary, and eventually they begin to feel more natural— at any rate, you're practicing normal drumset motions and orchestrations, so you will be improving, even if you don't feel like you are.
It takes a long time to learn this section of the book, and if you use my recommended practice sequence along with this voicing scheme, it takes even longer. You can't think in terms of mastering these materials— think of it more like physical training and just put the time in. If you're just getting acquainted with the book, it's probably a good idea to play just the individual 3 and 4 note patterns on pp. 15-18 and 20-21 for some time, and combine them later.
Oh, and you'll have a lot more fun if you use a practice loop. This is a great one: