Char cloth is cloth that's been reduced to charcoal that catches light really easily from a spark, but burns slowly so you can get a fire going properly. And I just made my first lot :D
Once the tin was cool, 10 minutes or so, I took the cloth out and tested a piece by sending a spark on to it from my magnesium fire lighter. It caught light with the first spark and slowly glowed away until the whole thing was burned. I managed to get the burning cloth to catch a few leaves alight just to be sure it really worked :D
The cotton cloth I used was cut up in to 2"x2" pieces and put in an old food tin. The top of the tin was covered with aluminium foil to seal it and a tiny hole in the centre of the top. I put the tin in the embers if my fire for around 10 minutes and let it smoulder away until the charring process was complete.