was at a fire demo where they had kids putting out gas fires with fire extinguishers, they used gas on a pan of water then lit it because the amount of gas was fairly small it burned controlled about 2 foot flames they were doing about a cup of gas at a time
and because of the water they could safely add more gas every time it was extinguished
this works because it was in the open , the pan was full even though most of it was water , the gas floats on the water and burns up any vapor is blow away
the important thing is that it be in the open away from things and that the pan be full so the sides don't catch vapor
the fireman was lighting it with a basic LP torch from up wind , I might tape the torch to a shovel handle just to be a bit further away but it didn't flare up on him just started rolling flames about 2 feet high and down wind
start small , but as you get it figured out I think you will find you can add more gas each time it burns out