This flick pattern is actually much simpler than meets the eye. Do not attempt to split the long flick pattern as this will give you a bad time. Simply do the entire thing with one thumb and shortly after reversing direction on your right thumb, begin with the left thumb and finish up the back and forth pattern.

For the 4 flick long fan I opt to split them as that transitions easily into the next note, but you can use any technique that works for you.