Have you ever JO while pissing? Sounds weird, right?
Here's how I do it. Build up a good piss. Stand in shower and get semi-hard. As I push to piss I start stroking. The pressure is unreal! Then fully erect I force my piss the whole time stroking, never letting up. It gives you the sensation of continually cumming. Then when you try to squeeze the last piss out, jerk strongly upward and you will be amazed how far it shoots up.
Sounds weird but try it!