This is how I practise my flow. I take any song with vocals on it. I try to copy exactly the rhythm and the pitch of the vocals. Then, I find the instrumentals for that song and try to scratch from memory. That's how I build up my flow. Nothing flows like the human voice, after all. Honestly, my flow is pretty much a collage of Organized Konfusion, Big L, Heltah Skeltah, and Redman. Copying exactly is bloody hard, though. Much, much harder than learning a particular scratch. P.S. not a fan of Tim Dog's flow.