Wait what? Pull back into a muscle up?
Kips on both apparatus should harness swing and NOT be muscling the skill. If you are muscling the skill especially with bent arms you are losing all of the benefit of learning the kip on hbar/pbars and on rings.
For hbar/pbars the initial glide is supposed to give momentum to load the body into the basket. YOu are supposed to ride the basket up, then forcefully apply hip extension with a downwards pull of the arms to use the power from the hip extension to counter rotate up to the top of the skill.
For rings, you can use the stretch shorten cycle to load the skill by starting in inverted hang and then 'bouncing' out of the basket with the hip extension. Same rule applies to forcefully pull the arms down and back to use it to counter rotate.
Arms stay straight all the time for all 3 apparatus.