1- a Hardware Flasher so you can read/write to the PS3 NOR flash
2- A Dongle with PSgrade payload (any old jailbreak dongle + PSGrade hex will do) used to Enter Factory Service Mode (FSM)
3- Rogero CEX3.55 v3.7 PUP
1- Dump the current NOR Flash of the bricked PS3 at least 3 times using a hardware flasher (Progskeet / E3 / TEENSY++)
2- Verify that it is properly dumped and you have a valid dump ready to be patched with the downgrade patches.
3- Patch the dump using Rogero PS3 NOR Auto Patcher or any other Program available.
3- Flash the Patched Dump back into the PS3 NOR using the Hardware flasher.
4- From this point you can continue as a normal Downgrade Procedure by entering Factory Service Mode using the dongle and Flashing Rogero CEX-3.55 v3.7 from the USB stick.
I own other 6 PS3 units but all of them have 3.56+ firmwares so i'm out of luck until we get a version that allow us to upgrade those. Also i own a OpenKubus... would that help me to use the PSgrade payload?