I have the latest BIOS (100). I use the F7 method.
I press F7 and the BIOS reboots. It then shows the typical screen again with the function key menu, including F7. This is confusing. If you press F7 after the reboot, the BIOS update fails. The function key menu shouldn't be displayed after the reboot, or the function keys should be ignored at this point. Failing that, the user should be informed not to press F7 a second time. This could be displayed on the screen or at least should be in the Bios Update Readme pdf file.
I didn't notice this reboot during update when I had BIOS version 70 and earlier, but I know it happens with BIOS version 85 and newer.
After figuring that out and doing it correctly by not pressing F7 a second time, the BIOS updating begins. The first thing updated is the Management Engine firmware. While updating, there is some action showing on the screen. It is the rotating bar thing. This is good. Unfortunately the subsequent updates do not show any action. This makes the user worry that these updates are not happening, and the process is hung. All the updates should show some action. Failing this, there should be no action on the screen when updating the Management Engine firmware because this leads the user to expect this action will occur on the subsequent updates.