I just did this yesterday --
I think in the beginning your in the mindset of doing it very carefully, therefore you end up doing it too slow. That's what I thought was necessary to make it recognize what I was trying to do.
So, anyway, after doing that a few times with no success, I started doing it more quickly. I figure on my successful attempt I did it exaclty about one key insertion/removal per second. Perhaps even a bit less -- it felt like I was going too quick, but it worked.
So maybe try the process a bit quicker.
Good luck.