Ive tried and tested loads of ways and the best ive found is to tip it upside down over a large seed tray or a tarp on a warmish day, and all the worms and bits will drop down. Then leave it for 24 hours. The next day, tap to get most of it out, and turn it back up the right way and pop it back as the top layer of the wormery. Pop a load of kitchen scraps in and move the top of your pile of castings over as the mass of worms should be at the bottom of the pile and scoop them back into the top tray.
Dont worry about getting it all out, the stuff that didint fall will have worm eggs or baby worms in it to replenish your stocks.
Any other way I find it just a nightmare.
I do have a very large seed tray which i use foe this. I have one of the large original round wormeries.
The other way I do it is to have a separate stash for maturing, and I just put the whole lot in there along with all the worms, and intersplice it with half tumbled compost and the worms finish it all off slowly over winter. I put these in small wheelie bins. The worms pretty quickly regenerate themselves and move up to the higher layers.
I never ever scoop all the wet compost out, I let gravity do the work.