It was a very difficult skill for me to master, but I refused to give up and finally, this year, I've gotten very proficient with it on my E36 anyway. I'm a very large guy with old football injuries in the ankle and poor flexibility. The key for me was getting custom pedals so that I wouldn't have move my foot very far for the throttle blip. Also helps to have good pair of racing shoes obviously.
http://www.ultimatepedals.com/
I ordered the full left side extension throttle, but ended up have to customize it further. Literally sat in my car with a marker on the end of a stick and outlined where my foot laid.
It is a glorious feeling to get a rev match spot on and being able to match the blip to how aggressively you're braking.
The pedals are still too far apart for me on the M4, so I use Sport for that car on the track for now. I actually think there wouldn't be that much difference in lap times for Sport and Sport+, both give full power and you have to modulate throttle with either one on corner exit. Traction is the limiting factor for either one.