Get an old used boot polish or boot dubbing tin (air tight metal ones). Clean it out. Store cotton balls soaked in White Gas in them. Use these as tinder. You shouldn't have a problem getting a fire started with these with a Ferrocerium rod and striker.

If your lighter is struggling to get a fire lit, then a rummage around in your FAK or toiletries bag, you might find a small pressurized can of deodorant or betadine. The pressurized butane propellant when ignited should help get a fire started especially with some hexamine tabs as your tinder.