one thing he says in the video is to concentrate on lifting with hamstrings and glutes. I think that struck a chord with me as when I think kick naturally I'm not thinking lifting. I definitely tend to not kick and as a result my legs sink more than they should.
https://www.youtube.com/watch?v=K7wwUweROI0
https://www.youtube.com/watch?v=K7wwUweROI0