Trying to master limb independence with J. Chapin's "New Techniques"

I'm working through Jim Chapin's New Techniques, and find myself having trouble with the section that makes the bass drum a part of the voicing. I can play the snare & bass drum parts with the HH on 2 & 4. But adding in the ride pattern (and really playing the pattern as opposed to just playing quarter notes) results in things falling apart. Even playing the pattern slowly can be a bear.



Unlike some, it takes me a while to develop the coordination and muscle memory when all four limbs are playing discrete patterns. Have any of you with similar challenges found a good routine or exercise for working through them?

Trying to master limb independence with J. Chapin's "New Techniques"