If your circumstances permit it (do you have 4 square feet of floor space in your home or garage or shed?), do yourselves a favor and make your own castings in a worm bin. It's the easiest thing in the world and, even when compared to Wally World's employee-exploitin' low low prices, it's extremely cost effective to maintain your own worm bin.
The worms do all the work! Look into it.
The worms do all the work! Look into it.