I understand that, but how do you packaged and prepare to send a firearm via UPS or Fedex? What about insurance? Payment type, do most peeps use paypal or something else?
Did you follow the link I provided, and read the info there?
The tutorial they have explains it all. It's not dependent on whether you use their service or not.
Basically, unless it's a FTF sale (check the legality for your state first!) the firearm
must go to a FFL. Legally, you are allowed to send it to that FFL on your own, but many dealers do not accept shipments from private citizens. Sucks, but it's simply a matter of CYA for the FFL.
If you ship on your own, you're going to have to use a common carrier - USPS is only legal for rifles and shotguns, as far as non-FFL's are concerned. Otherwise, it's UPS or FEDEX.
Your other option, and usually the easier one, is to have a FFL send it for you. That way, you're assured that it's going from a dealer to a dealer, and you're spared the hassle (and usually higher expense) of shipping it yourself. Also, tracking a gun that's gone missing or had an issue related to damage is easier to rectify when it's been shipped through a dealer than when one does it themselves.