Feed the cotton string through the hole to test the fit. It should have some resistance when adjusting the wick, but not so much that it shreds apart while pulling on it. Having a mile of wick is not necessary; as long as there is plenty of oil and the wick is thick, the cotton will not burn quickly. If your wick is thin, try braiding three pieces together to add to its burn time. Fanning out the wick and having a long wick will give you a brighter light but it will run down your oil and wick quickly. I use two bottle lengths of wick because I like to have enough to cut if the fanning of the wick gets out of control. When filling it up with oil, try not to fill it to the top, because the neck can get hot. Never refill when it’s hot, that’s why we make a lot of these before the trip so they can be set aside and a new one can be brought out. A twelve packs worth can be made in less than 20 minutes so there is no need to worry about refilling them and if you wanted to you could just toss them in trash when they are empty. These can be made on the spot, with the supplies on hand. An old t-shirt can be cut into strips and braided to make a wick. This is a useful thing to know for emergencies.