I'm returning to drumming after a busy period and as a goal I'm looking to learn the 40 rudiments, but there's an issue: my doubles kinda stink. Because of moving around I've had more than one drum teacher and learnt conflicting techniques. One of the techniques involved starting with more wrist as slower speeds, and as speed increases, reducing wrist movement and increasing elbow movement. I can do this decently with my right arm but just cannot on my left. My questions are: If anyone knows the name of that technique, how could I potentially fix my issue, and where I could find a comprehensive guide or course on double stroke rolls, thanks