Kipping pull-ups, when done with proper form should feel smooth and rhythmic. The technique described by @katibreazeal will also allow you to transition efficiently into either bar muscle ups or butterfly pull-ups within a complex without coming off the bar or losing rhythm. If all you do is butterfly pull-ups, try going back to the standard kipping pull-up from time to time. You will be surprised at how the recruitment from the lats is much more with the kipping pull-up versus the butterfly pull-up.
