The brass is a .45-70 case with the base cut off. The rope is 1/2” 100% cotton. Push the rope into the case and burn it to char. To light it I push the rope out some and lay it on the flint. A couple hits from the fire steel and it usually lights. Then I set the lit ember on the rope I to a tinder bundle. Blow the tinder bundle into flame like normal. To extinguish the rope, I pull it into the case and put my thumb over the tube to cut off the air flow.
The slow match can be used with char cloth too. I think of the slow match as a long burning ember. It’s less finicky.
I've been mostly using chared natural materials as of late. But never had any issues charging any cloth that was 100percent cotton. As stated already, my tins that aren't air tight don't get a hole.