when i try to tell the truth about Satan to people i start with " hey btw do u believe in aliens? " , and then i say " there are aliens who created us and are far more superior than us, their technology is advanced like hell and they can even telepathically communicate" and i just throw all those exciting and fun facts at their face then i start throwing the christian shit and how the those aliens split up because of humanity and how the ones who wanted to enslave humans named the allies of humans as evil and devil and how they created christianity. and at that point i tell him about Satan, before that i only say the name Enki.
Good luck .. ugh umm and yea , this method works good only if they doesnt know that you are anyhow related to Satan. coz they will already have the thougt that you are a freak and wont trust your words.