Its easy to store both cotton balls and petroleum jelly. You can either store them separately or together. It just depends on your preference.
Some suggest to smear the petrol jelly onto the outside of the cotton ball like these videos(1,2,3)
Others suggest soaking the cotton ball in liquid petroleum jelly (1,2
and still others suggest to just smear the petroleum jelly onto the inside of the cotton ball.
Each have pros and cons. Options one and two are messier than option 3 but option 3 inst has water proof as option 1(if smearing all of the cotton ball) and 2
Here is an easy and mess-less method of making petroleum jelly cotton balls.
It will last several minuets giving you ample time to put bigger pieces of wood on it.
The down side with this method is that it is not waterproof but if it gets wet you can always let it dry out.
Buy some waterproof matches and you won't have to worry about getting your fire starter wet.