School chemistry experiments. It's easy. All that's left is to move the contents from the balloon into a metal gas cylinder.
i.e. the hard part. That is if you want a convenience level approaching liquid refueling. Slow filling is an option, but there goes the one advantage over BEVs. That's...stupid. You are taking the natural gas going to the home, reforming it to hydrogen for a home fuel cell and to fill the car. There are efficiency and pollution advantages to the home power aspect vs a NG generator. Just no reduction of CO2. Well, slightly better but no where near the zero level hydrogen proponents claim. Then there is the refilling the car aspect. Honda did this with their NG Civic, but had to tell people to stop using the system. NG going to homes was just dirty enough to rust out the cars' fuel system. I'm sure this won't be an issue with the hydrogen, but that NG system had some pricey annual maintenance costs for the pumps. Hydrogen cars fill to higher pressures than CNG ones, so that is still there, and likely higher.
I don’t care how much money Toyota throws away on hydrogen hype, as long as the government isn’t subsidizing it