Summarize this article:

Rub a cotton ball into a bit of petroleum jelly. Use your fingers to work the petroleum jelly into the fibers of the cotton, thoroughly coating the entire piece. You could use a cotton makeup pad instead of a cotton ball, if desired. Either option should work well. Grab the cotton ball or cotton pad with a pair of tweezers and slowly lower it into a pot of melted candle wax.  Work carefully to avoid accidentally burning yourself on the wax. Coat the majority of the cotton, leaving only a small patch uncovered. Place the coated cotton on a sheet of wax paper and let the wax on the cotton cool and harden. Place the coated cotton in a plastic bag or plastic container. Keep them there until you are ready to use them. Make sure that no moisture can get inside the container as you store it.

Summary:
Dip cotton balls into petroleum jelly. Alternatively, dip the cotton into melted wax. Store the firelighters in a sealed container or bag.