Can't say I've ever had the need or the desire to play double strokes.
Actually to be perfectly honest, it was the first time I saw Infernal Method play that I KNEW it was possible to play bullshit fast with single strokes. So that's basically what I've practiced for years and years. I've made a whole CD (40 mins worth) of a click track that starts off medium kinda paces, and jumps by 5bpm intervals every 5 minutes... I just sit at my practice kit and go as far as I can. Which ever speed I get sloppy at, I go back, and do the one before it again a few times, and keep progressing. Seems to work for me.
Then once I'm feeling pretty good I'll practice along to something like Fear Factory's Demanufacture and see what I can do. Quite demoralizing.
