It depends on how you are restoring your flash.
If you are using an e3 flasher, rename the dump.swap.bin to bkpps3.bin and flash in fun mode.
If you are using Progskeet, use the original dump and flash with Winskeet. Doesn't matter what it is named.
If using multiMAN, use the original dump. I am not sure if it has to be named specific or not? I haven't flashed back from DEX before. I like my DEX console still. And have other PS3s for the new CFWs.
If that is what you are doing, going from DEX to CEX. Don't listen to me. Follow this the last part of this guide