I was using fire place ashes and screening the char from ash. Then, put it in a pillow case and smash them with a rock and hammer. You don't want to bust up your side-walk doing this! Then, you can charge it and add it to your compost. I think that char is more important when you have low organic matter, like ground soil. Also, you should ask
@DonBrennon about using too much char. I think that he is still around?