If ether must be manually applied to something, my preference is to "shoot" the air filter for half a second to one second. (Some of the new "safer" cans spray a lot less than they used to...) It really does not take much, only a "whiff". The idea is that you need only enough ether to "help" the regular fuel light on that first time around. If you need more, you've got a lack of fuel problem that needs fixing, not spraying.
Anyhow, using the air filter as a "storage area" gives a lone individual more than adequate time to walk around the vehicle and start the vehicle without rushing, as well as forcing the ether to evaporate, greatly reducing the opportunity to get too high of a concentration in one cylinder. and the subsequent damage that is possible when that happen.
Lots of folks insist that you have to open up some intake plumbing to get the ether "close to the engine". I disagree. Ether does evaporate but it does not go away. The intake is a closed system. You WANT AND NEED it to be fully evaporated when it hits the engine. In a closed space, evaporation is way different than dissipation, which happens in an open space.
The factory kit injects ether through a nozzle, in a carefully measured and remarkably small amount, and it does it in a positively metered fasion. (Pull the switch to "charge" and release the switch to inject, you can't vary the dose). Ether works or it doesn't. Just a whiff is all it needs and therefore all it releases.
I like the idea of spraying it out the passenger windshield as well. That is probably as good as you can get to guarantee "ingestion" of a bit of vapor, without allowing too much at once.