downgrading 3.72 using pandoras battery

alright so i wanna downgrade my psp i have 3.72... my brother has 3.5 firmware and i would like to use his to run homebrew to then make a pandora battery to thus downgrade my psp i would like to know what i would need to downgrade his psp i know i need the lumines game how do i know if its patches or not?? any help would be appreciated. thanks