Downgrading

Hello,

I haven't been following the news about PS3 Downgrading for a while and I have some questions.

1)Can i downgrade from any firmware? I have checked that my console supports 3.55 firmware.
2)Should i use e3flasher or progskeet?
3)Which is the latest firmware version and which release should i use?

My ps3 is a Fat cechl 04

Thank you