I agree, flaring is manageable.
You have to put the right amount of gas in the priming well initially. Too much and it will flare up. Too little it won't heat it up enough.
If it's too little, no big deal, when you turn it back on, liquid will come out instead of vaporizing. Just turn it off and let this burn which will then properly heat it up.
And you have to get the hang of turning it back on when the priming fire has gone down but not out. Or else you'll have to re-light it but there could be a little cloud of vaporized gas that could flare up.
The worst time is when it's hot - like if you turn it off for a bit, and then turn it back on. Liquid fuel will hit hot area and vaporize creating a cloud of vaporized gas. Light that and poof!
You just have to let it cool off a while before re-lighting.
When it flares up, it quickly burns out. Just keep your face away from the area above. I don't think it would burn long enough to catch your tent on fire. Always assume it will flare up.
Use it some in the open to get the hang of it before using in vestibule. You should get experience with all of the above so your response becomes instinctual.
Or, for a canister stove, turn it on, light it, put on your pot with liquid to heat up, when liquid is heated up enough turn it off. This seems easier.
Unless it's below 25 degree F or so. I've done the copper wire around canister and up into flame down to 20 degree F and I think that would work even colder but that's where maybe WG becomes the better solution.