After your “red wigglers” have digested the bedding and food scraps you have fed them (usually about 6 months) you should have enough castings to harvest them for use. Stop adding scraps until all is eaten. At this point, you will wish you had two bins. Remove any paper bedding that might be left in the bin.
Empty the bin onto a plastic-covered table, or on the ground, outdoors, or under a bright light. Make a long low mound and slowly scoop the casting off the top of the mound. The worms will quickly bury themselves, diving toward the bottom of the mound. Continue removing castings until the worms are left with a thin covering. Put them back into their bin with fresh bedding.
You are ready to use your new casting in pots and in your garden. Sprinkle a handful of this nutrient-rich material in potting soil for houseplants and layer an inch around vegetables and ornamental plants. Mix it into the top layer of soil and water it in. Cover the enriched soil with a layer of mulch. There will be worm eggs and a few young worms in the castings. Try to remove them but 100% removal is impossible. Some may be able to live through the winter in temperate climates with dried leaves or wood chips sprinkled over the soil surface.
You can put a small amount of worm castings (about 5%) in seed germinating mixes. I use one part worm compost to four parts potting mix for seedlings and mature plants. Even though this is a high ratio, I have never burned potted plants with well-composted worm casting.
“Worm juice” that runs from the spigot at the bottom of your commercial worm bin is sometimes called “worm tea”. It is extremely beneficial to plants. I dilute it with water at a ratio of 1:4. You can make worm tea by putting worm compost in a cloth bag and steeping in a bucket of water for a few days. Remove the bag and water your plants with this “lovely liquid”.
I’ll add pictures to this post the next time I harvest.