I put egg cartons (paper, not styrofoam) in the containers slightly buried in substrate. A lot of the worms either climbed into the cartons or hung out just below them. When I wanted to collect some I lifted the cartons and grabbed a handful of worms. You have to act quick or they'll just burrow underneath again. What are you giving them to drink? I gave mine apple slices and they also liked to hang out under them. Repeat checking under the stuff everyday for 5 days or so and you'll get most of the worms out. You'll end up getting mostly worms, but also some bedding, which isn't an issue since you'll want to put them in the fridge with a bit of bedding anyway. Just find out where yours hang out. I purposefully left a few in and continued feeding them and everything. I found that they usually turn into pupae on the surface so it's a lot easier to take them out than the worms that burrow. And if you miss any of those, they'll turn into beetles which are easily moved to the breeding container, usually before they lay eggs. Anyway, hope this helps and good luck!
I will definately go for a captive bred scorpion (or mostly anything, for that matter ).