I'm finding 0.6.7 a bit more challenging than any previous versions, trying to get it to work without bootstrap is something I've decided to turn into a weekend project in case I really b0rk things up.
That was in OC 0.6.6, but anyway it's pretty easy.
Set LauncherOption to Disabled, boot into OC picker and reset NVRAM, after that set LauncherOption to either Full if you used Bootstrap before, or Short if you used BootstrapShort. Reboot again and done.
1) Make sure I have a backup of a working EFI folder from the current working release.
2) Copy the new OC files over the existing EFI directory
3) Manually open my existing config.plist and the example config.plist from the new OC version in propertree
4) Carefully go through, checking and comparing for new entries, or removed entries - takes about 10 minutes.
5) Having edited my config.plist as per step 4, check it for sanity at: https://opencore.slowgeek.com/ (currently only at 0.66)
6) Reboot & cross fingers!