Hi Azzo,
I've prawned at the Entrance a few times with some good success.The basic process is to wade out to about waist deep water with a hand net and prawnlight and stand still in the outflowing tide and scoop up the prawns as they try to swim past you out to sea. You need to head to the Southern bank at the carpark there just east of the main town. When the prawns are on you'll see quite a few other people down there so just follow them out and see what they do, they were all pretty friendly the times i was there In terms of when to go, from what i've seen you want to head out any nights from just before the new moon and through up to about a week after as this is when the prawns make their run out to see. Lastly, you'll see lots of blue swimmers heading out to sea as well, avoid taking these as they are females heading out to sea to spawn.
R