Two fingers, one switch
Butterfly clicking splits the work: index and middle finger alternate on the same button so neither has to wait for its own recovery. Done well it reaches 600–950 CPM, and it stays cleaner under load than jitter because it spends coordination rather than tension.
The cost is rhythm. Two fingers at slightly different rates produce a run full of doubled and dropped presses, and the per-second chart shows it as alternating tall and short bars.