Payments and registration when selling a car privately

(SZ) I'm hopefully selling my car, and I'm wondering what the common way for payment of 30,000 SFr is. Seems like a lot to carry around in cash for both buyer and seller. I'm guessing Twint would be a fun one, but does that accept large amounts? Do people go to bank tellers to do this, or how does it work here?

I'm getting conflicting advice on Fahrzeugausweis. The most direct one seems to be to go together to Verkehrsamt so the old one can be cancelled and the new one created all at once? I need to call them, but any suggestions and gotchas would be interesting to hear.