Here'as what you gotta do: USE YOUR IMAGINATION!!!!

I write about many gruesome deaths, (i have a character that is really into it and pretty much does it for pleasure) so i think i know what i'm talking about. You don't need someone to tell you how to describe such a death. You can do it from the killer's POV, from the victim's, from both's or as a mere witness [make sure the killer doesnt see you in that case :)]

It's all about your mind and the way you see things. if you really want minute details, imagine you are the victim; imagine waht you think would be a gruesome way for you to die, something that really scares you only to think about it.

or imagine how would you like to kill somebody you really dont like.