There are several usable methods. Besides carrying a bic lighter my favoured back up method is to also carry a flint/steel and small pack of tampons. They come individually wrapped in cellophane that helps keep them dry and can be 'teased' open to a good size. They also light every time from a spark. You can coat them in a petroleum jelly type product that will make them burn a little longer if you want but they work ok without that.