as far as I know, you don't need to do anything. I would get a bill of sale of some sort just in case the gun is ever used to commit a crime seeing as they will come to you first. I think a gun store can do a legit trade and re-register it, but it cost a fee.
Ideally there are quite a few people that would rather buy used due to it not being registered in their name if the government were to ever revoke the right to bear arms.
I have sold and bought guns with nothing more than a handshake and an exchange of money for goods. I didn't check ID, I didn't ask for an LTCH. I simply asked if they were a resident of Indiana and if they were a proper person.
Ok, and I promise I will not have any weapons eitherur under citizens arrest. meet me tomorrow for your incarceration.