Having flown both, practically the difference between the two is absolutely minimal in flying. The 747-8 is designed to simulate flying the -400 (stop laughing in the back those of you that have done both).
I doubt there will be any manuals worth reading that will make your life better.
The big difference is electronic checklist discipline. And unfortunately no manual in the world can teach you that. You just need to practice it and learn the one giant gotcha (sorry I won’t tell you what it is, i’ll leave that to your procedure trainers).