if selling in state,,, you can private sale
if selling out of state,,, you need a copy of the dealers ffl that you are sending to, and make sure it is an ink signed copy and it is not expired. also, if you are shipping from an ffl, you will need to have your dealer send the recieving ffl a copy of his. As I understand the law, and I have shipped many weapons, only the recieving dealer ( who you are sending the weapon to) needs to have an ffl which like previously stated, you need a copy before you ship.
also, ups, usps, or fed ex will all ship long arms. I would suggest you get insurance on it just in case, and a tracking # as well.
if I missed anything, anyone feel free to chime in but I believe that is it
there ya go