When i do it, i pull the PCV out, and put that right on the mouth of the bottle. Its a perfect fit in the opening.
And i would suggest to do it on a slightly windy day, so you can just run the gas in your driveway/road and let the smoke get carried somewhere else.
(i'm lucky to have a backyard with no-one in it... by time it gets back there, its pretty well dissipated)