My cotton ball w/ Vaseline method is to put a handfull of cotton balls into a ziplock sandwich bag - make sure they are 100% cotton with no synthetics. Then add a good three-finger glob of Vaseline (I use the Walgreens generic stuff). Purge the bag of air before sealing. Then massage the bag until the balls are evenly coated.

You want the outside of the balls to be well coated, but the insides to be a bit dry. When lighting with a match or lighter, fluff the ball up a bit. When lighting with a sparker, try turning the ball inside out so that the non-coated fibers are available for lighting. They should take a spark pretty easily. I tend to use two balls at a time to start a fire, but if I was resource limited I'd likely drop it down to one or even part of one.