The Ko brothers have done some videos on practice and instruction. Not all of them have English subtitles. Here's their channel on YouTube:
https://www.youtube.com/channel/UC7Tq7qBiEmUQH25vg3R-b7g/videos
https://www.youtube.com/channel/UC7Tq7qBiEmUQH25vg3R-b7g/videos