ShootTheCore
Legendary
As long as your kit isn't one of the initial batch of CPS2 Multis then you can update the firmware by just placing the file on the root of the SD card. You will still need to solder 3 wires for the key programming afterward though.
If you do have one of the initial CPS2 Multis then you'll need to use a Discovery programmer to update the firmware. I can loan you mine if you like.
If you do have one of the initial CPS2 Multis then you'll need to use a Discovery programmer to update the firmware. I can loan you mine if you like.