The only thing required to transfer title on a car is the signoff on the back of the title itself is my experience. Regardless, it wasn't just the car thing. I was really speaking about anything of value that is bought/sold.... It's not a problem for me if someone won't do a BOS on a gun they want to buy, because it won't be one they get from me if I ask for one.
That is a bill of sale. Just handing over the car for cash is not a bill of sale.