I had the same problem but figured I just use the side of my foot and not the heal. As long as you can blip the throttle before the turn holding the brake, down shift and lift off the clutch u good to go. You have to get a feel for it not to upset the balance of the car. It took me a while to get used to it, so practice practice practice. I practice every day I drive the car. Ya every day. After a while I don't even think about it just comes naturally. Check this video out from the
MASTER. I have watched this video about ...... shit lost count.