You can use the latest Flash Utility to flash both 1st and 2nd generation drives. It cannot get any simpler than that. Rest assured that the other methods work too, only that they are more complicated. They have been all tried and tested many times already, so we know for sure that they work just fine if the instructions are followed correctly.
If the drive is a 1st generation drive, it will work just fine with both 1st and 2nd generation firmwares. I’ve got a 1st generation iHBS212 drive which I have been running for many years now with the latest 2nd generation PX-LB950SA firmware on board.
Any 2nd generation firmware will work with any iHBSx12 drive, irrespective of its generation (but not vice-versa). What is not possible is to flash a 2nd generation drive with a 1st generation firmware.
Could you post a copy of this firmware please?