Yup, charcloth is probably your best bet, with a few tutorials around the web and on here.
Next up might be some finely fluffed amadou -
made from prepared "Horses Hoof Fungus" -(Fomes Fomentarious), Chaga Fungus -(Innonotus Obliquus), or possibly Cramp Ball Fungus -(Daldinia Concentrica).
A
Biologist rant alert The latin species names have to parts; the genus and species. So Fomes fomentarius is of the genus Fomes and within that genus the species fomentarius. One always uses a capital first letter for the genus, and never with the species. Also, preferably, an italic font.
If your going to the toruble of making charcloth then why not just use cotton wool?
With a flint and steel I've found charcloth catches a spark much easier than cotton wool. It also smoulders so allows you time to catch tinder, I've found that cotton wool burns too quick if you only use a small piece.