Here are some videos about sticksmash.
Trainer serves succession 2 high shuttles.
The student returnes with 2 sticksmashes.
Comments for this video:
By 2 fast consecutive shuttles the student is forced to keep the racquet up after 1. beat. This promotes the rebound effect.
The student in the video would have to swing the racket less and rebound quickly. Swinging back the hand of hot stove plate can serve as a visual help.
These were his first attempts at this technique. In the meantime, he does it much better.