That's fundamentally different than the Video Copilot tutorial because you aren't breaking one layer down to reveal a background plate. You're working with 3-4 layers (the flaking skin, the arm, and the body. The bg being the fourth layer depending on what's going on). I would also think you'd have to wrap these particles in 3d. You could try something in a 3d suite like 3DSM or Maya, but if you haven't shot yet you may want to consider doing it in a practical manner with layers of liquid latex.