Yes. I used the blocked chord technique.
This is good in the initial stage to learn the notes, but to play the middle section of this impromptu up to standard, it may be just what you have to get rid of, especially if you don't have really huge hands.
Instead, use a "walking hand/arm" approach from finger to finger (like walking with your legs) with NO attempt at all at holding or preparing full positions. Instead of going heavily downwards into the key, create the sensation as if you are pushing yourself up with each fingertip.