2. Develop and learn to control the (explosive) kip
Efficient kip is what will get you through higher volume of chest-to-bar pull ups. Start swinging your feet backwards and forward, from global extension to flexion (hollow position), while maintaining tension throughout your body.
Kipping is about coordination, controlling the movement and keeping it in a certain, efficient rhythm which creates weightless momentum when you can “pull” yourself up with using less strength than with a strict version. The power generators in this phase are the hips and the core, and the explosiveness of the kip depends on the force produced (with it). Chest-to-bars need a stronger kip, more power generated to bring your body higher.
See Carl Paoli’s video for bar kip progression.