Cashiers checks still work just fine. The big thing to avoid is selling it to anyone who wants it shipped to them in another country. Or someone who is buying it, having it shipped and you never meet or see the person.
Local transactions require the buyer and seller to meet in person, for them to exchange driver’s license info, fill out a release of liability retained by the seller and the title, retained by the buyer. This really cuts down of fraud because if someone wanted to steal your car, it’s easier to just steal it in the night as opposed to sharing identities and letting you see their face.
Cashiers checks that large often require a thumbprint of the person cashing it and they have to go into a bank (either their own or the one it’s drawn on) and they are on video cashing it. Scammers like none of that. Scammers like western union, as soon as you hear the words “western union or wire” get suspicious.
I would never pay in actual cash for a private party car. If I get to the dmv and find out the title was a fake and they just sold me a rental car, what recourse to I have. But if I bought it at their home, saw the inside when we filled out the paperwork, copied down their drivers license number on the title and gave them a cashiers check so I will have their thumbrint and picture if they defraused me, I’m covered. As a seller, I dont expect people to be rolling with 10k in $20 bills, cashiers check is fine, if it ends up being a fake, I report my car stolen/embezzled and my insurance takes over, but one again it would have easier for them to just steal it, now I know what they look like, their phone number. Even dumb crooks know there are better ways to steal than that.