I was faced with out of state buyers wanting my cruiser but luckily a local guy bought it.
If at all possible- fly or drive out there to do the transaction.
if that's impossible, pull whatever strings are necessary to have someone you trust do the transaction in your absence. I had a local guy check out my cruiser for his friend on the east coast.
If that's impossible, from what I've heard, automobile escrow services blow and are to be avoided. Real estate escrow services won't touch it (too small fry).
The last and worst choice is talk to the seller extensively on the phone to get a feel for what he's like - and if he seems cool, trust him to ship you the vehicle when he gets paid.
But in the end it has to come down to trust. If nobody trusted anyone and everyone was a crook, we'd all be living behind sentry walls with rifles in hand ready to shoot the next passerby.
If you look around you, your home, your town, your city, your state and your country.... It was all built on trust; People trusting each other to carry out their end of the agreement.
Yes there are crooks amongst us, but most of us aren't— it's always a gamble.