Wah lao... they severely lack a crab eating culture...
Try to throw the whole live crab into the pot...never scrub/wash, never remove gills, never remove bladder and other innards...
Chinese fast method is to open the abdominal flap, then drive a chopstick through the anus (cause this part the shell is weakest) to stab into the heart and nervous system.
The claws and legs will go limp. Now can pull off the abdominal flap, dig thumbs into the space between where the flap was attached and the carapace, then using both thumbs and the impaling chopstick, pull off the carapace.
May still see the heart beating, but nervous system is gone.
Yes, it can be squeamish. But I believe everyone needs to do this at least once to understand and properly appreciate the enormity of killing another animal so that we can eat its carcass to feed ourselves.