jphughan got it right, albeit long winded (j/k). I was used to heel-toe in mostly Japanese cars where the pedal is hinged at the top. I didn't get the hang of the BMW until I kept my heel on throttle pedal on the floor. Then everything fell into place. Of course, I had been doing heel-toe for years. Putting the throttle into sport mode helps but after you get the hang of it, shouldn't be necessary.
In any case, practice. Going to an HPDE and having an instructor with you can help. Even better, go to one of the "racing" schools and they will drill it into you, so I've heard. Don't expect all your shifts to go perfect. But when it does, it's like sex.
I've been assimilated. 6MT/ZPP/18"/PS extended.