The bootload is done after the boards are assembled. I don't know of a solution for putting a bootloader on the chip without soldering it to a board first. I would not care if I had a bootloader or not until I was successful getting the chip soldered to the board...Soldering and making the board is the hard part in my opinion. I built 10 small arduinos but, only 8 accepted the bootloader. I have yet to fix the issues with the reamaining 2.
As far as loading the bootloader goes, it is the same procedure as working with the dip 328.