The key is to keep the pot constantly moving up...there's nothing keeping those shrimp in your trap besides the flow of the water as it comes up, so you can't have pauses or let it rest once you start to pull.
Very important detail here for those pulling up pots by hand! You need to keep the pot moving upward (so the shrimp are held in the trap by the movement of the water), 'cause every time you pause, they can swim out of the pot.
(voice of experience here... you don't want to drag a pot up from 300 feet only to see it empty).