It's possible. I can't remember which version of NVflash I used, but I am pretty sure I tried all three (NVflash, ID mismatch and Certs bypassed). I did brick one of the three vBIOS''s, but was able to restore it back to stock using a GT710. Using the protect off string can help to flash on cards with protection, but does not always guarantee success. If you are going to brick the card, it can usually be saved regardless of whether you use protect-off or not.
The naming scheme doesn't really matter as long as it's simple and you know the correct one and do not accidentally modify your stock file. My vBIOS folder looks like this:
Reboot or shut down does not matter as long as the computer restarts following a flash. I was never able to find the correct driver version to run the XOC bios he listed, so I stopped at restoring my one corrupted vBIOS switch and moved on from trying to mod it. I was able to change the frequency tables, but I never could increase voltage or wattage on my 980 or 980Ti.
I honestly can't remember which version of NVflash I used to successfully flash the 980. It was one of the 3 below
NVIDIA NVFlash with Certificate Checks Bypassed v5.287 Download | TechPowerUp
WWW.TECHPOWERUP.COM
This modified version of NVFlash lets you flash a modified BIOS to your NVIDIA graphics card.
NVIDIA NVFlash with Board Id Mismatch Disabled v5.590.0 Download | TechPowerUp
WWW.TECHPOWERUP.COM
This is a patched version of NVIDIA's NVFlash. On Turing cards, NVFlash no longer allows overriding of the "board ID mismatch" message through comm
NVIDIA NVFlash 5.792.0 Download | TechPowerUp
WWW.TECHPOWERUP.COM
NVIDIA NVFlash is used to flash the graphics card BIOS on Ampere, Turing, Pascal and all older NVIDIA cards. NVFlash supports BIOS flashing on NVID
I hope you have better luck than I did.