A bloody ghost happens when you are going on a girl after you have already jizzed on her back, achieving superman status.
Then you pull out just before you blow a load in her bearded clam, and right after she turns around to give you a blowjob, you jizz on her face. Typically she is stunned, and that is when you punch her in the face.
Thus, at last you have achieved the bloody ghost.
I fucking pulled a bloody ghost on Sandy last night and caught her by total surprise when she didn't get one in her stench trench.