Here is my European Nightcrawler bin that is about 6 weeks old. I started it with 50/50 precompost and plain shredded cardboard. As you can see, the majority of the bin is worm castings! So cool!! At this point, you have options. You can sift castings and reset it with more fresh worm bedding (My go to is that 50/50 mix) OR you can do what I did in this video.
I am not in a hurry to sift castings, so I was ok with doing this option. I split the bin in half, and put half in another new mortar bin. Then I added dry shredded cardboard to both of the bins and mixed it all in. The castings had a LOT of moisture, so the dry cardboard was able to soak up a lot of that moisture to help it not be too dense or muddy anymore. The worms are very happy with this because it put air pockets back into the bedding and gave new cardboard for them to start munching on. Splitting them also gives them more room to spread out and grow.
These worm castings will inoculate the fresh cardboard and the microbes will start latching on to it. If i was wanting more worm castings, I would have sifted this and put that 50/50 precompost and cardboard. Remember this turn around was 6 weeks. It usually takes months and months to get worm castings from just plain cardboard. Precompost is the way to go!!