Just thinking ahead as I’ve not currently got a decent pump available – I’ve got a small pump with a screw in hose which is presta at one end and schrader at the other. If I manually pumped up a wheel with schrader valve to a decent pressure, then attached the hose to the presta on a wheel I’m looking to inflate tubeless, then screwed the other end of the hose to the inflated wheel with the schrader valve, would that work to inflate the tubeless wheel quickly enough? A bit like the lemonade bottle concept.

Unlikely- not enough volume in the ‘donor’ tyre

Car tyres work….

Too much pressure in the car tyre though? Otherwise, that was actually my first thought!

Too much pressure in the car tyre though?

Not enough, to seat some tubeless tyres it seems.

You’d need at least 65psi in the donor tyre. Don’t think there’ll be enough pressure differential for them to equalise quickly enough to pop the tubeless one up though.

I use a ghetto 2L bottle inflator and pumped up to 50psi it inflates a tubeless tyre from zero to about 25psi. The pressure differential is the key, as it’s the speed of the airflow that blows the tyre onto the rim, not the duration of the airflow. So a smaller volume at 100psi is better than a large volume at 25-30psi

Edit- with reason. A road tyre at 100psi probably won’t work!