Well for firesteel or ferro rods you are fine with any sharp hard object... you are scraping of shavings of the ferro rod that ignite in the process.
For traditional flint and steel, the "steel" is more important than the flint. In this process you are shaving off bits of the steel striker which inturn ignite, creating sparks. The steel needs to be high carbon and very hard (58RC and above) Your 1095 David Farmer definately has the carbon content but depending on how he heat treated it, may not have the hardness. Many makers draw back hardness on the spine to gain toughness in a knife. though the edge may be 58-62RC the spine may only be at 52-54RC... maybe even lower. Which makes for a better knife IMO but incapable of traditional Flint and steel fire lighting.