One of my students is a Metal drummer, which is kind of unusual for me. Part of our lesson time is workshopping methods for improving his double bass drum technique. I’ve had him do a lot of ordinary stuff, played with both feet in unison— regular funk grooves. This drill involves combining 8th notes with both feet in unison, and alternating 16th notes, using pp. 22-27 in Syncopation.
These seem to be the crux items:
Play each thing many times, along with the cymbal/snare drum ostinatos. His main one is the unison 8ths, but there are some other possibilities. You can also isolate one part of each exercise so one foot always leads. Whatever it takes. Obviously we’re going for speed, endurance, and control here.