Its hasnt changed.? You can still do face to face private sale. The people must not have any reason to believe the other party involved is a felon and/or cannot legally own a firearm.
Some states don't allow FTF sales, California for example requires the sale to go through an FFL and the FFL holds the firearm for I think 10 days.
When did FTF, in state, sales become illegal?
I've always understood that you only had to (by law) do a form transfer if you went through/bought from an FFL dealer.