I use at least an ounce or a little more, then let the warmer set for a few minutes to let the fluid soak into the wedding. It uses the fumes to stay burning.

I have had to hold a lighter on the catalyst for a short time on warmers that have not been used in a while, but never had one not light after a few tries.

“Two things are infinite: the universe and human stupidity; and I'm not sure about the universe.”
― Albert Einstein