I also have a hard time learning to double-pop. I've seen those instruction videos by Vic several times, but his hands ain't mine and he isn't left handed playing righty as I am (
AFAIK). I just don't have that coordination in my right hand...
The hardest things regarding double-pops are to me to get the timing right for both pops and to make them sound similar. After the first pop with the index, the ring finger instantly wants to mute the string before popping it the second time. Is this accepted or should I work on letting both pops ring out properly when I practice?