In English, “good and [adjective]” means “very [adjective]”, so “good and dead” means “so richtig tot”. 
Thank you, learned something new! I don't think I have ever come across that idiom.
The same happens with me and German. I’m fluent (but it’s not my native language) and I occasionally encounter new idioms as well.
Upon further reflection, I think an more precise explanation of “good and …” would be “totally …”, in that the idiom implies completeness, thoroughness, and finality. I think the most common phrase you encounter is “I’ll do it when I’m good and ready”, meaning they’ll do something once they’re
thoroughly prepared and not a moment sooner, also meaning that they won’t let themselves be rushed.
Like in this comedic dialog at 3:40:
https://youtu.be/0C-9DLDCmjAAnd apparently there was even an eponymous 90s pop song:
https://youtu.be/XYx7zV-IcB4