a error free method is undiscovered. the best one that is less dangerous is dean's. using MM to flash. as I am told it only flashes part of the nor/nand instead of the whole thing. seems to work for some and bricks others.
mystery element is still a unknown. but more and more people are starting to talk about bricking when switching back to CEX to watch DVDs or blu rays or just to go back to normal.
My advice, Just wait. Devs around the block have been working on it to make it easier for everyone. just takes some time. Soon we should see a better linux free solution. ( right now it requires the ps3 to be on 3.41 -i think- ) and maybe a solution for the DEX to CEX. or a better understanding of it. right now I have heard that it has to do with qa / syscon / hash checks / firmware versions.