So there's no confusion about meter: in jazz parlance 12/8 is a meter, but it's also a feel. These exercises are all written as 8th note triplets in 4/4, which is basically exactly equivalent to 12/8— there are twelve 8th notes per measure in 12/8, and with these triplets we're also playing twelve 8th notes per measure in 4/4. They're both counted in 4, they both have a three-note “triplet” subdivision. This isn't the time to go into detail about it; just play the triplets and don't be thrown when I refer to it as a 12/8 feel.
I've put together an easy little set of methods, using Progressive Steps to Syncopation by Ted Reed. Pp. 6-7 and 10-11. We'll be playing the book rhythms with the triplet grid filled out in a way that should be very familiar, and adding several stock cymbal rhythms. For example, using the rhythm from page 6, line 7:
First way: Play the top line* on the bass drum, and fill out the triplet grid with your left hand on the snare drum:
* - 99% of what we do with this book is based on interpreting the top line, and ignoring the bottom line, even on the two pages where the bottom line is the same as the top. Let's move on.
Second way: Play the top line on the snare, and fill out the triplet grid on the bass drum. Except here, when there are multiple runs of bass drum notes, we'll put in a rest on the beat. So you're only ever playing the last two notes of the triplet on the bass drum— “John Bonham-style”, as it's known on the internet:
Also use the exercises from pp. 10-11. To get the practice rhythm, swing the 8th notes and fill in the middle note of the triplet. Quarter notes are handled the same as before. In the examples we'll use the line 5 rhythm:
First way: Bass drum-lead, fill in triplets on snare drum with left hand:
Second way: Snare drum-lead, fill in triplets with bass drum:
Keep reading— the actual practice routine is after the break:
Practice routine: Play all of the exercises (including the 16 bar exercises) from those four pages of the book, each of those ways, along with the following cymbal-and-hihat patterns:
1. A shuffle rhythm:
2. A quarter note triplet rhythm, written here as parts of 8th note triplets:
4. And with two beats of each, which is our so-called “Afro Blues” rhythm:
5. It's also an excellent idea to play them with just a straight triplet rhythm on the cymbal:
Before running the complete system with any given cymbal pattern, I suggest warming up with exercises 1, 14, and 15 from pp. 6-7, and exercises 11, 14 and 15 from pp. 10-11.
I see I haven't posted any practice loops in 12/8 on the site, so you'll probably have to make your own. This isn't a particularly fun method to play with just a metronome. I use Lopsy Lu.