The beaches around Redcliffe don't hold beachworms, more other types (rockies, blood). I would have thought the ocean side of Bribie would hold them, but have never tried. I think that would be your closest Northside spot.
We used to spend most weekends in Yeppoon catching beachworms using tinned sardines with a couple of holes in the bottom to bring them up and then used a piece of cheese in the shape of a wedge. As the worm raises its back we slowly placed the wedge in front of it and it gradually crawled up the wedge. This is a little easier to get your fingers either side of the head / body ... especially for beginners.
Good luck,
Stewie.