make sure you buy real cotton cotton balls, there are some synthetics that dont burn well. get a ferro rod, i have used a buch of different kinds, from the walmart 5 buck magnesium block rods to the fire steels and strike forces, bigger the rod more and larger sparks you get. the walmart mag block rods can fall out so put some epoxy on them if this is going to be your emergency fire starter. some folks melt the vaseline in a pan and dip them in the liquid then make up a whole bunch at a time, the liquid is pretty flamable so be carefull if you try this method, i would not do this in my house. i just take a dab and rub it in to the cotton balls.
some folks push them into large plastic straws and seal the ends, then cut them open if they need them.
i put it on light rub it in good, and keep the cotton balls in a film canister, easy to carry and the film canister holds a ton more than you will need. you can get a fire started with 1/2 of a regular cotton ball most times. if it is real wet you can burn 1 then light a second from the first and extend the heating time to dry out damp tinder. they will burn for about 3-5 minutes, giving off enough heat to get your kindling/tinder bundle going.
i have held them under water for 30 seconds shook them off and they are easily lighted with a fire steel or other ferro rod. just fluff up the fibers so the sparks can contact some of the fibers and they will light. i have used the saw blade on my SAK to fluff them like a comb, then used the back of the saw blade or the can opener blade (dont use you knife blade it makes it dull pretty fast) to scrape the ferro rod.
some folks break off a stick and then twist the broken end into the cotton, this makes a large lolli-pop, light the cotton and them use the stick handle to move it under their kindling/tinder bundle. i taught my 10 year old daughter how to make a fire with this method in a heavy snow storm and temperatures around 10 degrees. give them the knowledge that may someday save their life.
alex