I've heard of people finding red wriggler worms at walmart I certainly can't vouch for them. I ordered mine years ago from an online retailer of worms and they've done well for me. They arrived in a little bag and I was uncertain if they'd make it, but they did!

As for the castings, I use a five gallon bucket full of water, into which I put a couple "double handfuls" of castings. This I mix up along with a bit of molasses and then I put an aquarium bubbler into it and let it bubble for a day. The next day I use it.

Check with your local county extension agency for worms -- mine held a vermicomposting class, and if you paid a little $$, you got a ready-made worm bin, complete with worms.

@ Dave, What would happen if I didn’t bubble it? What exactly does the bubbler do?
@ Mary ~ thank you for the idea to check with our local extension~ great idea

@Toni

Toni, the bubbling brings fresh oxygen into the mix. Without that the water will quickly turn stale and it'll tend to rot. The oxygenated water is vibrant with life and has a wonderful aroma.