based on my own personal past experience as a recreational re-enactor and semi-professional LH interpreter who smoked a pipe, (with LOTS of relighting--of course back then pipe smoking was not considered unacceptable "in character") charcloth that is too tight or finely woven tends to let the glowing steel sparks bounce off and not ignite. coarser and looser textured material tends to catch and hold the glowing curls and chips of metal and ignite much better.
The best material I ever found was some old pieces of worn and very weathered canvas that had been left behind after a storm interrupted re-enactment festival. I believe it was a tentage fragment of 100 percent canvas. with it a could get fire on the first strike almost without fail. I really hated to see the last of it go.
the flint and steel pipe lighting was done as an "unconscious" thing in the course of my presentations and always distracted the audience, which naturally lead to an explanation, discussion, demonstration of flint and steel, fire starting, and a demonstration of flintlockery