Have you got some marshmallow fluff and a microwave?
You need a CFW PS3. To install CFW on a PS3, it needs to be on 3.55 OFW. The only way to downgrade to 3.55 OFW is with a hardware flasher. (E3 Flasher clip for NOR, teensy++ soldered for NAND.)
Or, you could just buy a PS3 that's already on custom firmware, though, that takes the fun out of it ;3