Yes you can use coco for bedding, just keep the lights off the worms don't like light.
Worms feed off of decaying matter so you probably could burry like two chopped up old tomatoes, or kitchen scraps ran through a blender to help the decaying process.
About two cups of blended scraps will feed for about a week maybe two.
Also with the coco bedding you can mix a junk mail letter or two with it for their pleasure. I raise red wigglers worms but night crawlers I guess all the same except diet. My worms will eat anything just about absolutely no salt.

Don't let it get to moist and maybe rinse the coco some for PH issues or the worms will try to escape if not happy. Worms regulate their population if they're happy they grow in pop. But if not happy they die off. Keep at room temp too.

Buuuttt if you get a microscope and look into the bedding your worms came in you probably will see all kinds of things moving gnats, mites, etc., not harmful to you they like what the worms are doing. It's like they live with the worm population.

Hope it helps